Note 1: Late UK cars seem to have a subdivision of the green circuit with its own in-line 35 amp fuse supplied by the white/brown (ignition relay) circuit feeding things like heated rear window, turn signals, heater fan and tach, which leaves the original green circuit fuse (2nd one up in the four-way fuse block) feeding things like reverse lights, stop lights, washers, wipers, and circuits associated with the seat belt warning lamp and time delay buzzer.
Note 2: The bullets for the reversing light grounds also contain the wired grounds for rubber bumper (and 1974 North American with split rear bumper) number plate lights.

Location of the reverse light switch on a 3-synch gearbox ...

... and a 4-synch UK (74.5 to 76) gearbox: