Hi there, Steve500 again.
James is probably correct, if the door is locked shut you don't have access to the x2 self tappers in the door jambs.
Just to conclude my own problem (drivers door opens OK from inside, but does not release from outside).
I bought a full new drivers door locking mechanism and took it to my local mechanic as I could not undo the x2 45mm 12 star screws in door-face.
He whipped off the door card, window glass and simply adjusted the linkage from outside handle to lock!
Bit of a struggle but he charged me only for 1/2 hour labour.
Also please all ignore the youtube demonstration of removal of door handle in 1min 36sec with a piece of bent wire - the guy in fact only removes the plastic trim from the door handle! I know, I tried it.
(New o/s drivers door lock for sale, bnib, cheap).
Happy tinkering,
Steve500