Can anyone please please give any suggestions as to the cause of my central locking problems (P Reg Mondeo Mk II TD) - It's driving me mad!

If I unlock the driver's door with the key, normally the other doors stay locked, occassionally the rear door on the driver's side opens. If I lock it at this point (with the key in the driver's door), only the drivers door will lock.

Sometimes when you go over a bump, or slam the door, the rest of the doors open, but not always. Once they have all opened, if I lock the car (again with the key in the drivers door), all the doors then lock.

The buttons on the key don't work at all.

Any suggestions will be greatly appreciated...