Two issues with central locking - any help/suggestions welcome

Firstly, Some time ago my boot (tailgate) stopped unlocking/locking with the rest of the central locking, I was told that this was down to the electrical acutator. So got a new one (only a few quid), but that hasn't really solved the problem as it how locks/unlocks only some of the time.

Secondly, the car has drive away locking activated, but the one of the rear doors tries to lock but doesn't (button goes down then up again), most of my jouneries are on the motorway, so this isn't that much of a problem, but around town it tries to lock this door every time you go over 20kph.

Any ideas, so where is the central locking ECU, or is it part of a body controller, located?

Welcome to Briskoda. For starters, have autolocking deactivated to get rid of the annoyance from the rear door. It only takes a couple of minutes to do with VAG-COM software but it does help if you live near a member with it.