Well, tell him he's not alone!
Put my remote in Saturday, connected wires up according to Haynes wiring diagram and the remote manual....
Just freakin' Haynes got the colours wrong, instead of the ignition +12V I wired up the bottom stock micro switch for the lock with the result that it unlocked by itself immediately after locking.... Took me a night's sleep until I finally realised what I'd done

Now I know not to trust the Haynes' and only look in there after I'm done with the job

So for who-ever has this issue if you have a mk3: the ignition 12v line in the central locking loom in yellow-green not yellow-red (or red-yellow which is the micro switch for the 'closed' position.