if so first check is the fuses then check the connections to the lock (you'll need to remove the rear door trim panel first) after that it gets expensive. The lock is about £300
OK. Half an hour, a can of WD-40 and some Spray Grease and it's freed up a treat - all whirring merrily away now. A bit of moisture in there - I assume that was the problem. All cleaned and greased now.
Had trouble getting a look at the mechanism as everytime I moved it I triggered the central locking! Nightmare, but sorted. Removing that mechanism must be a complete cow.