Hiya, i have the same problem on mine. The drivers door has been like it ever since i got the car back from a monkey of a so called mechanic. Now i find that the passenger door has now stopped working just 2 days ago. They will lock with the fob, but not unlock. The two doors will also not lock with the 4mph speed locking. very annoying.! Poppy.
if its not the above, then theres a possibility it is a dodgy door latch assembly or actuator... dont think theres a problem with the system itself otherwise the back doors wouldnt be working... which they are, the system doesnt appear to be as complicated as some newer cars which have an actual module in each door.. but these cars dont appear to have that looking through the wiring diagram.
so if it was any kind of serious electrical problem all doors wouldnt work, passenger door and 2 rears are linked together.. so if it was any kind of problem with the BCU it would knock the 2 rear doors out as well, and drivers door operates on an independant circuit because it has the microswitches in the door lock barrel.
so whatever the problem is, its likely to be local to the drivers door, and passenger door.
Also because they are the most used doors, its more likely to point towards a worn latch mechanism.
in the case of your problem poppy, I dont think the problem with the 2 doors is related.. drivers door went first because its the most used, then passenger door after because its less used.. backs are ok because they are probably used even less.
They do go, ive had to change 1 before on a rover 200, in that case it was other way around, door wouldnt lock properly so the alarm kept going off, and when i pulled the door latch mechanism out, there was alot of play in the part of the mechanism connected to the actuator.. so it was effectively jamming up, stopping it from properly locking.
only way to identify them problems would be to pull the door card off and see whats going on inside there.
Will keep investigating and post any more findings.
at the moment im just theorising to try and find a logical explanation. lol.. so i could be completely wrong... but worth checking though none the less!