I too built a Scotch mount in the 1970s, Nick. I was surprised how well it worked for time exposure photography. Mine was always “fully manual” with its hand-turned screw.
This was more successful than another project from the JBAA: to build a small planetarium (I think the inspiration was a paper by Harry Ford). I used Meccano for the equatorial support which held an electric motor to which was attached a ballcock. The ballcock contained a lightbulb and there were holes to project the constellations. It never really worked and heaven help anyone who tried to recognise the constellations.
A slightly more successful project was to build a lunar photometer, using a photocell, from a design by Chris Watkis. Chris lived not too far away from me, in Sevenoaks, and was a great help. I can’t remember if this was in JBAA, the Lunar Section Circular, or elswhere.