why is my central locking not working?

I thought the battery in fob key for my corsa was the problem, I changed this and tried re setting it by putting key in ignition etc, still no joy.If I put the key in lock and turn it will open driver door only, if I put key in lock, turn and press the fob all doors open, Is this a problem with the fob or the central locking module in the door?. The fuse has been checked, but is there another fuse for the central locking system, please help.