Hi all, thanks for the advice........it's fixed!!!! I removed the passenger door card so I could study how the mechanism worked first. On the drivers door i was able to lift the card away at the top rear, just enough to see the solenoid. After removing the trim panel on the B post i had just enough access to be able to remove the small screw halfway down the edge of the card. With this out i was able to pull the card away quite a bit more.
I could then see the problem, the part of the mechanism which moves down onto the lock cam was barely moving. I just pushed down on the cam with a large screwdriver and the door opened!!!! hoorah.
I could see no obvious reason for the malfunction, so copious amounts of LM grease were applied to the internal mechanism and the catch that connects onto the B post. Everything now operates nice and slick. i suspect the mechanism was just sticking (it had been a little stiff for a month or so) and my hamfisted f*cking around with the pop-up knob pushed something out of line.
Anyway, it is possible to gain access to the solenoid and lock mechanism without any damage to the door card. The only casulaty was the brown plastic shield by the solenoid which had to sacrificed so I could see and access the parts
Thanks everyone, Paul