I was having alot of trouble with the central locking and the actuall door lock itself, but after trawling the forums I found Colin Colin Abraham
BMW Central Locking - Fault and repair
This guy now's what he's talking about and he fixed my GM5, the door lock and ordered a new electronics board for the key fob.
Any probs with the central locking give this guy a call.
I would just like to say a big thankyou to Colin.