Well thank goodness I haven't damaged the Flux Capacitor.
These holes are on an '84 Revell Romany (a local London builder). The bike is a tourer in the mould of the Dawes Galaxy et al. The holes aren't threaded and they actually enter at a lead angle. I think the generator idea is definitely the most likely. I've never seen one before, must have been and gone during my 'fallow' period.
Yes, the shifters are Suntour Power shifters and they are a definite improvement on the pure friction shifters of my youth having said that I still hanker for a pair of Campy bar end shifters; they were the bees knees in my day.
Thanks all