The Main Measurements you will need are:
Backset: 28mm & 35mm Centre: 70mm  

Ferco Multipoint 2 Roller Latch Only will lock your door with a single turn of a key and is ideal to be fitted to most UPVC doors..

Specifications
Sold with a one piece lock, clockwise latchbolt and two roller cams
Operation :
When the handle is lifted the two roller cams will engage into the strikers. The handle will then return to the horizontal position.
With a turn of a key this will deadbolt the latchbolt and this will ensure when the handle is moved downwards the door cannot be opened as the roller cams are engaged
The lock is then disengaged by turn of a key and when the handle is moved down the bolts are removed from the strikers and the handle will then return to the horizontal position

Please specify the size of the backset which you require.
28mm backset : Faceplate stamped 5.28
35mm backset : Faceplate stamped 6.35
Handle furinture to suit : movable pad/lever with 70mm centres & 7mm spindle