Finally I have managed to assemble all the electronics for the Crunchie Boost and try it out with my guitar. It certainly sounds tube-like and pretty much does all I planned, however, there is some distinctly annoying hum. I think it just needs shielding better but also I have decided I will need to get a +9V power supply rather than using my -9V one "in reverse" since there are definitely some grounding issues. This is a shame as it means I can't run it off the same supply as all my other pedals but meh, could be worse.

I will post some recordings of how it sounds as well as some geeky waveform analysis at some point. But for now here's a picture and the complete circuit diagram...