In desperation, i opened the car and, with the alarm blaring, disconnected the battery. I reconnected the battery and did what you do when youve replaced the key fob batteries which is to unlock the door with the key then to press the lock button on the fob 4 - 5 times and it locks and is operational as normal.
It just shows that, as with computers it's worth "re-booting" as it often cures the fault.
Thanks to all who helped!
Alastair.
