Following some of the really helpful advise previously given on here, I sorted out the loom in the tailgate as some of the wires had corroded and broken; all good.
Unfortunately, and this may be totally unrelated, the bimmer won't lock using the key fob but will unlock and open the boot. I've had the fob checked out and everything appears normal there meaning it's something in the car, no?
I have heard that there are two relays responsible, one to unlock and one to lock, worth checking them out? Any previous experience or advise is greatly appreciated.