I did use a voltmeter when searching for a hot wire in that connector so, I will take that all apart again and look again, maybe I missed something.
Did you see the switch I photographed for the Forum? What is it?
Distant memory, but I have a feeling the one in your photo is not the reversing light switch. That has green (ignition switch feed) and green/brown (switched feed to light) cables connected to it, and can be found on right hand side of gearbox.
