Hi. I have exactly the same problem. Firstly you need to do a series of tests. Firstly, check all your fuses in your fuse box. Next, put the key in the lock and turn it. If it still turns through its full motion then you know its not the barrel. Next, try and unlock the car from the passenger door. If the driver side door unlocks then you know your central locking pumps and mechanisms are working. If you have got this far then your in the same boat as me. there is a small lever attatched to the end of the barrel that turns with the key to activate the entral locking. this is probably snapped and needs replacing. I'm not sure where to get it from or who specialises in repairing it, or if its easy enough to do yourself. All i've found is that the lock is a bugger to remove.
Alex, October 2007