Just to add to this thread, scud, do the windows work on that door? If not, it could be something to do with the control unit in the door (The one attached to the window motor) rather than the lock motor. It may have gotten water into the big multiplug and corroded. Same goes for the plug on the lock motor.

If the windows work, then it can't be a problem with the wiring from the body to the door, as the windows and lock both use the same power/canbus wiring.

However, it PROBABLY is the lock that has failed, and is quite commonly a dry joint where the 6 pin connector mounts on the PCB inside the mechanism. Like pikpilot said though, if the motor sounds graunchy, it may be mechanical.

Oh, and the door open warning light is probably the microswitch in the lock, oor a dry joint on the connector.

The window works fine but the lock is still intermittent even after a soaking with wd40.

Think I need a new lock motor, anyone got one?

That graunchy sound often means there is a dry joint - the motor is running at reduced voltage and it's struggling