Key Won't Central Lock
 

A mate at work has a W plate 1.8 75 saloon.
He's having probs with the key fobs.
He can't lock or unlock remotely.
He has 3 keys.
All 3 will start the car and allow him to drive.
All 3 have new batteries.
To unlock the car he uses the key in the door lock.
Once in the car when he presses the central locking button by the handbrake the central locking locks and unlocks all the doors, so the fuse and the central locking system is ok.
Have any members got any idea what the problem is and how to solve it?

Press the big button 4 times in rapid succession to re sync the key.

Try a battery reset...( I assume no sat nav)