how do you replace the barrel in a upvc door lock?

The last answer will not work. If the key is lost the cam naturally will prevent the lock from being removed without the key. There are one or two methods to remove it but you need locksmith tools which you shouldn't be able to obtain to do it.

A locksmith shouldn't really charge more that about £40-£50 to replace it.

John L
May 2007

On the edge of the door,you will see a screw that is slightly larger than any others fixing the locking mechanism.(sometimes you may need to remove a cover plate.)
Undo this screw,(it is usually about 2" long) then you will be able to slide the cylinder out from either side. this type of lock is called a EURO CYLINDER. There are several different lenghts, so take the old one to B&Q ou similar for a replacement
See page 233 of a SCREWFIX catalogue. or

Keith Howard
May 2007

Check previous answers.

Big Softy
May 2007