I want to replace the lock cylinders on a set of uPVC French Doors. The
doors look the same except the slave door has an extra section added to it
which forms the join between the 2 doors. (I'm assume I'm using the
master/slave terms correctly - the master door opens first).

Replacing the cylinder on the master door looks easy as I can see what looks
like the retaining screw, but what about the slave door? There's a multitude
of screws on the edge of the extra section fitted to the slave door. None
looks like its a retaining screw, so I'm assuming I have to remove some of
these to remove the central section from the slave door. I assume this will
give access to a door edge which will look like the edge of the master door
and will have an obvious retaining screw for the cylinder.

Can anyone who has done this confirm that this is the method? Any pitfalls
in removing the central section which is attached to the slave door?

Thanks in advance if anyone is able to help.