I had a problem once similar to yours, it opened but bleeped but wouldn't lock or via the key and the dash display said doors were open, I had to change the drivers door central locking mechanism as I traced it to that. After I replaced it, it worked perfectly and I didn't need to program anything, all Rover 75 and ZT mechanisms are the same from memory. I took the old one apart and found a small plastic lever had moved to where it shouldn't be so the lock wouldn't work properly. I put that part back, put it another car and it started working again. The bit I'm not getting is it works after disconnecting the battery until you start the car but you may want to try changing the drivers door central locking mechanism as that could be faulty as per mine, there are a couple on ebay at about £65 (as always the drivers door is more expensive) or if you have a breakers near you you may get it cheaper if you want to try that, to change the BCU you might need the car T'4ed and one that will talk to the innards of the car but sometimes a normal T4 doesn't work on 260s as I've been told a few times by those who have a T4 computer. There are also different BCUs depending on if yours is a facelift or not