How can I change this lock?

[Ballllzac]

I’ve lost a key to the front door of our flat so want to change the lock in case the key falls in to the wrong hands. I’ve done this before with a straightforward barrel lock but not sure where to start with this one... any suggestions?!

So far I’ve figured out that it’s the europrofile cylinder sash lock linked below, so presumably I can change the cylinder, but I’ve no idea how to get at it...

www.doorhandlecompany.co.uk/eurospec-universal-replacement-euro-profile-cylinder-sashloc-19662/?gclid=EAIaIQobChMIwNK2m6XS6gIVyu7tCh1hWQyoEAQYAiABEgIfyvD_BwE

Tells be an Allen key bolt on the handles and the thumbturn.

Undo these, then unscrew any face plate from the door

There might also be a cover around the door handle which is normally will pop off.

I was hoping there would be a simple solution. Thank you @walksen!

in your link you show a lock case. You don't need a case, just a cylinder.

From what I can see, your cylinder projects out of the door, which makes it easier for a burglar to snap it. you can get anti-snap cylinders, but consider a protective dorhandle plate which surrounds the cylinder and makes it difficult to grab or snap.

Otherwise, measure the lengths (from the fixing screw) of both sides of your cylinder and see if there is one a bit shorter that can be used. Cylinders are ordered by the two lengths, e.g. 30mm/30mm, 35mm/30mm etc

examples

It doesn't matter about the inside projection, as you have a thumbturn, for emergency escape.

Some photos of your doorhandles will help.