OK, so getting the lock switch out from the rubber mounts is very messy requiring cutting and melting the rubber mount that covers the switch terminals. I ended up destroying the donor as my soldering iron tip was a bit ham fisted. My original lock must have been an earlier revision without the rubber though steps require taking to stop the metal corroding.
This pic shows my replaced switch soldered in and working 100%
https://goo.gl/photos/fozznygHf5mqNz288
This shows poor donor
https://goo.gl/photos/oEhEAcQn4h79fHWN8