Ford Mondeo, 1998 1.8 TD LX Central Locking Problem?

So here's the issue. The Key Fob for the remote stopped working yesterday after gradually getting a bit 'sleepy'. I presumed the batteries were at fault, so i bought some new ones and it hasnt solved the problem.

I'm at a stage where the car will not respond to the key fob being pressed. The drivers door can be locked/unlocked with the key but the rest of the car's locking system doesn't respond. However, it can be locked/unlocked centrally from the passenger door and all doors lock and unlock.

I've reprogrammed the key to the car already, that went fine but i cannot get the remote locking to work....

Any suggestions would be greatly appreciated.

Thanks
Duncan