I built a speed controller years ago (don't think it was a Maplin kit) so my mate could use his big angle grinder as a car polishing mop. It had pretty good torque control. It would would work VERY slowly and was still pretty unstoppable?
It has only failed once (in the 10 years since I built it for him) when the noise filter in the IEC socket failed. I replaced it with a non filtered socket and off it went again ;-)
All the best ..
T i m