1) When I bought my 2004 RR the OS rear door wouldn't unlock with the central locking, reaching back and pulling the inside handle unlocks it fine, and locking the car with the remote fob does lock the door. This is an issue I've lived with for a couple of years - constantly thinking I'll get round to it one day.

2) During this time, the NS front door lock refused to unlock, this panicked me and I read a lot of threads about having to rip the door card off to get to the locking mechanism, then one day it just popped up, so I took advantage of this to remove the door card safely, then replaced the locking mechanism the following weekend (Phew).

3) I had quite a lot of work done in the engine bay causing the car to be at a garage for well over a month, when it came back, the drivers door became erratic on locking and unlocking using the key fob, sometimes it does, sometimes it doesn't.

4) Now the NS rear door lock is behaving exactly like the OS rear door, it will lock using the key fob, but to unlock I have to manually pull the inside handle.

Are RR central locking systems just hopeless or could there be an underlying issue?

As additional information, you can hear the lock motors operate on all four doors when you press the fob (Either locking or unlocking).

I haven't stripped any of the doors yet (Other than the passenger front which currently is the only one working as it should).

Any advice / tips before I set about taking it all apart?

My experience has been that older cars do suffer from rear door locks sticking, it happened on my 2004 car. Cleaning and lubrication was the answer there, but maybe renewal is necessary in bad cases. Only Range Rovers since 1988