I didn't get any replies to either of my posts so I carried on regardless. The door lock that wouldn't undo, I took the door panel off from the inside of the vehicle, without damaging anything, completely removed the window motor and other fittings, loosened off everything on the lock that I could and wearing a thick pair of gloves I rocked the lock assembly rather forcibly backwards and forwards until it broke in half.
I then ripped out the broken bits and whilst doing this the door unlocked. After that it was easy.
I replaced the door lock with a unit from Ebay for £28:00.
Th unit I fitted started to play up after a few months, with other lights apart from the door light, coming on. I bought another unit for a similar price and fitted it and It apears to have solved the problem. The original supplier refunded me without any hassle. It apears to have solved the problem.
I worked in Zambia for the Land Rover dealer in Kitwe for a few years back in the 1970's and the door locks on those were a lot easier to replace.