There are at least 4 earth wires in that loom if I recall correctly, so that your alarm wire could find an earth in that area of loom without the switch being involved.
https://www.the-t-bar.com/forum/54-how-tos/92793-how-to-change-a-door-lock-mechanism
It's OK You're not going blind.
PS as it seems this is a common fault on TFs, if I buy a 2nd hand lock, is there not a fair chance it will be faulty too, or will go that way in the near future...?
That is true. It is a game of numbers and luck ...
Oh great. As Basil Fawlty said “I’m so happy.”
Does this micro-switch also operate the internal light when the door opens…?
In other words, do I need it at all…
OK, modified approach… I took the car out today for a good thrash, couple of hours, fast, slow, stop, start, open the boot/close it again, over bumpy roads etc, and no sign of the boot warning light coming on, so I cautiously suspect my diagnosis of a bent spring contact in the boot lock, which I absent-mindedly straightened again, was the cause of the warning light coming on.
However, during the period when I isolated the switch completely, the alarm still went off once, so I suspect two problems. The car only has 14000 miles on it, so I’m going to take the view at this stage that the volumetric sensors are more likely to be responsible than the door switches – so will lock it with the key every night, and pray for the neighbours.
Just one thing… where are these sensors? Can’t spot them anywhere…
I was not aware that you did not lock only by key when you were trying things. I assumed that you isolated volumetric sensor during testing period. If you did not, then, as you said, I would also suggest to do so and see if that is the problem, before attempting to do anything on door side.