Lewisham Locksmith Service Team
Local locksmith team
15 Jul 2026 13 min read
Most people assume that if something goes wrong with a lock, the entire lock must come out. In practice, that is rarely the case — and understanding the difference between changing a cylinder and replacing the whole lock mechanism can save you time, unnecessary work, and the disruption of a bigger job than you actually need. Whether you have just moved into a flat in Lewisham, had a key go missing, or are dealing with a damaged uPVC door lock, the right fix depends on what type of lock you have and exactly what has gone wrong.
This guide walks you through the two main options in plain terms: when a cylinder swap is enough, when the full lock case or mechanism needs to come out, and what each job actually involves. We cover the most common lock types found on front doors, back doors, and flats across Lewisham and the wider south-east London area — including 5-lever mortice deadlocks, Yale-type nightlatches, and the multipoint locking systems fitted to most uPVC and composite doors.
## Cylinder or Whole Lock: Understanding What You Actually Have
Before you can decide what needs changing, you need to know which part of your lock does the work. On a uPVC or composite door — the kind fitted to the vast majority of modern homes across Lewisham, from the terraced streets around Hither Green to the newer blocks near Lewisham town centre — the working part is a euro cylinder. This is the oval-shaped barrel that sits in the centre of the door and contains the key mechanism. The multipoint locking system itself — the hooks, bolts, and rollers that engage with the door frame — is a separate component built into the door slab. If your key turns but nothing happens, the multipoint mechanism may need attention. If the key no longer turns, or the cylinder has been damaged or snapped, the cylinder is usually the culprit and can be changed independently.
On a traditional timber front door you are more likely to have two separate locks working together: a Yale-type nightlatch near the top and a 5-lever mortice deadlock lower down. The nightlatch has a small cylinder on the outside face of the door that can be changed on its own. The mortice deadlock is a different animal — it sits inside a pocket cut into the door edge, and its mechanism is the entire lock case. You can sometimes change the cylinder on a mortice lock too, but the lock case itself must be removed if the internal mechanism is worn, damaged, or no longer meets the BS3621 standard that most home insurers now ask for.
## When Changing the Cylinder Is Enough — Lock Change London Made Simple
A cylinder swap is the right call in a surprising number of situations. You have moved into a new property and want to know that no previous tenant or owner holds a copy of the key — this is one of the most common reasons people ask whether they should change the lock on a new property, and in the UK context the answer is straightforward: the standard British approach is to swap the euro cylinder or the nightlatch cylinder for a new one. The lock case stays put; only the barrel that reads the key is replaced. The job on a euro cylinder typically takes a matter of minutes for an experienced locksmith: the single retaining screw is removed, the old cylinder slides out, and a correctly sized replacement slides in.
A cylinder change is also the right fix after a break-in attempt that targeted the cylinder without damaging the door or the multipoint mechanism, after a key is lost or stolen where you cannot account for all copies, or simply when an old cylinder has become stiff and worn. If your door is a uPVC type and you are upgrading for security, this is also the moment to fit an anti-snap, TS007 3-star rated cylinder — a worthwhile step given that cylinder snapping remains a real method used by opportunist burglars in residential areas across London. The cylinder is the weakest point on most uPVC doors, and swapping it for a quality anti-snap version is one of the most effective single security improvements you can make.
## When the Full Mechanism Must Come Out — Door Lock Replacement London
There are situations where the cylinder is fine but the lock itself has had it. The most telling sign on a multipoint lock is when the door handle drops, the lock feels loose or sticky in a way that is not related to the key, or the hooks and bolts no longer line up with the keeps in the frame. Multipoint mechanisms have many moving parts, and after years of use — or after a forced entry attempt — the gearbox inside the mechanism can fail entirely. In that case the whole multipoint unit must be removed from the door slab and a matching replacement fitted. This is a more involved job: the door needs to be measured carefully, the correct mechanism sourced (they are not universal — dimensions, hook spacing, and backset all vary between manufacturers), and the new unit fitted and adjusted so the door closes and locks smoothly.
For a 5-lever mortice deadlock, the full case needs to come out when the internal levers are worn, when the lock has been drilled or damaged during a break-in, or when you are replacing an older lock that does not carry the BS3621 kitemark. Measuring matters here too — the backset is the distance from the edge of the door to the centre of the keyhole, and getting this right ensures the new lock case fits the existing pocket. If you have ever wondered how do you measure a backset on a mortice lock, the answer is to measure from the edge of the door (the part that faces the frame, also called the door stile) straight across to the centre of the keyhole. Common backsets on UK mortice locks are 57mm and 76mm, though older doors can vary. A professional locksmith will take this measurement as a matter of course before sourcing a replacement, so nothing needs to be guessed.
If your door lock has been damaged in a break-in or a lockout, calling a professional is the right step before attempting anything yourself. Our team covers Lewisham and surrounding south-east London postcodes around the clock — call 020 3757 5731 and we will send someone straight out, usually arriving in around 30 minutes.
## uPVC Door Lock Repair London: Cylinders, Mechanisms, and Common Faults
uPVC and composite doors are the most common type of front and back door across Lewisham, and they come with their own set of specific faults. The euro cylinder can be replaced as described above — but it is vital to get the size right. A euro cylinder is measured as two numbers: the external length (outside face to centre of the fixing hole) and the internal length (inside face to centre of the fixing hole), written as something like 35/45. Fitting a cylinder that is too long leaves exposed metal on the outside that can be gripped and snapped; fitting one that is too short means the cam will not turn the mechanism properly. A skilled locksmith will measure both sides of the door before selecting the correct cylinder.
Beyond the cylinder, the most frequent uPVC faults are a dropped handle (usually a failed gearbox inside the multipoint mechanism), a door that will not lock from outside even though the key turns freely (often a snapped or disconnected spindle), and a door that is stiff to lift the handle on before turning the key (a sign of misaligned keeps or a tired mechanism). Lubrication solves some of these; parts replacement solves others. If you are unsure which you are dealing with, a locksmith can diagnose on site and explain exactly what is needed before any work begins. For combination-style electronic locks on communal entrances, the process of how do you change the code on a door lock or how do you change a combination lock code varies by brand — some use a physical reset button sequence, others require a digital interface — but the principle is the same: access the programming mode, enter the current code, then set the new one. If you are locked out of the programming mode entirely, the lock may need to be replaced or factory-reset by someone familiar with that model.
## Emergency Locksmith London and 24 Hour Locksmith London: What to Do Right Now
If you are locked out in Lewisham — whether from your flat, your house, or a communal entrance — the first sensible steps are always the same: check whether a window or back door has been left on the latch, contact a neighbour or family member who may hold a spare key, and if you are a tenant, try your letting agent or managing agent who may hold a set. These options take moments to rule out and cost nothing. If none of them apply, you need a professional — not a workaround that could damage your door or give someone else access.
What you should not attempt is forcing a lock open yourself or trying to work out how do you pick a door knob lock from an online tutorial. Beyond the risk of damaging the lock, latch, or door frame, attempting to bypass a lock on a property you cannot immediately prove you occupy can create complications with neighbours, managing agents, or the police. A trained locksmith will verify ownership or occupancy at the door — this is standard practice — and then use the correct non-destructive technique for your lock type. If the lock cannot be opened non-destructively, they will explain why and confirm what the replacement job involves before proceeding. As a 24 hour locksmith London team, we are available every day of the year, including evenings, weekends, and bank holidays. The price is confirmed with you on the phone before anyone sets off, so there are no surprises. Factors that affect your quote include the type of lock, the time of day, travel distance to your postcode, and whether parts are needed. Call 020 3757 5731 — we answer 24/7.
## Choosing the Right Fix: A Practical Summary for Lewisham Homeowners
The short version: if the key mechanism is the issue — worn, compromised, or simply needing a security upgrade — a cylinder swap is usually the right and quickest fix. If the mechanism that actually throws the bolts or hooks is faulty, damaged, or no longer adequate, the full lock case or multipoint unit needs to come out. And if you are upgrading from a standard cylinder to a TS007 3-star anti-snap version on a uPVC door, that is a cylinder change job that delivers a meaningful security improvement without touching anything else on the door.
For anything beyond a straightforward cylinder change on a door you have full access to, it is worth having a professional assess the door first. Lock types vary considerably — even on similar-looking doors on the same street in Lewisham — and fitting the wrong part, or misdiagnosing which part has failed, means doing the job twice. Our team carries a range of cylinders and lock cases and can carry out most jobs in a single visit, day or night. We cover Lewisham and the surrounding south-east London area as a fully insured, experienced mobile locksmith service. Whether you need a cylinder swap, a full door lock replacement London, a uPVC door lock repair London, or urgent help after a lockout, call 020 3757 5731 and we will talk you through the options before anyone sets off.
Frequently asked questions
Do you need to change the lock or cylinder when you move into a property in the UK?+
In the UK, the standard approach is to replace the cylinder — the barrel that reads the key — with a new one. This is simpler and equally effective. If the door has a euro cylinder (common on uPVC and composite doors) or a nightlatch cylinder, a locksmith can swap it quickly. The lock case stays in the door and the existing mechanism continues to work normally, just with a new key. This means no previous occupant, tenant, or keyholder can use their old key.
How do you measure a backset on a mortice lock, and why does it matter?+
The backset is the distance measured horizontally from the edge of the door — the face that meets the frame — to the centre of the keyhole. On most UK mortice locks this is 57mm or 76mm, though older or non-standard doors can differ. To measure it accurately, open the door and use a tape measure from the door edge straight across to the middle of the keyhole opening. Getting this measurement right is essential when sourcing a replacement lock case, because a lock with the wrong backset will not fit the existing pocket in the door edge without additional work. A professional locksmith will always take this measurement before ordering or fitting a replacement.
My uPVC door handle has dropped and the door will not lock — is that a cylinder problem or something else?+
A dropped handle on a uPVC door is almost never a cylinder problem. It is usually a sign that the gearbox inside the multipoint locking mechanism has failed — the gearbox is what transfers the handle movement into the hooks and bolts that secure the door. The cylinder and the key may still work perfectly. In this case the multipoint mechanism needs to be replaced, not the cylinder. A locksmith can confirm this on site by testing the cylinder separately from the handle and inspecting the mechanism through the door edge. The correct replacement mechanism must match the door's brand, dimensions, and backset precisely.
How do you change a combination lock code on a communal entrance, and what if you are locked out of it?+
The process for changing a combination lock code varies by manufacturer and model. On most mechanical combination locks, it involves holding a reset button or lever while entering the new code sequence; on digital models, you typically enter the existing code first, then follow a programming sequence to set the new one. If you do not have the current code or the lock has been set by a previous managing agent, you may not be able to change it without a factory reset, which usually requires physical access to the inside of the lock unit. If you are locked out of a communal entrance and cannot contact your letting agent or managing agent, a locksmith can assess the lock and advise on the safest way to restore access — call 020 3757 5731 for help any time of day or night.
