XJ40 Cenral Locking problem

[jimthack180]

I've just purchased my first XJ40, and the central locking has gone mad.
When I picked the car up, it worked fine, but since I got it home, it won't lock at all, just keeps setting the alarm off. I resorted to just leaving the car unlocked all night, but then it wouldn't start next morning, just dead, then, after several trys, suddenly it started. However, when I got to work, it would'nt lock, as before. The battery is fully charged. Both keys have the same effect. The previous owner says he had no problems, and it must be something I've done. Any ideas please?
Car is a 1993 Sovereign.

[robv12]

try locking it on the key from both front doors and see if all the buttons stay down, if they do the system is working ok, if a button stays up that door solenoid has failed, if when you unlock and a button stays down that solenoid has failed, if you lock it but it refuses to lock it will be one of the front solenoids failing OR a door lock mech seizing up

If the system works ok on they key, but not with the remote, it is the remote that is at fault

i have lock mechs, soenoids and remotes here if needed