It works! Had a couple of days off so got more done than I thought I might. Had a problem with the blend, it was acting as a master volume. Retired another pot in and now all good. Still lots of setup to do, but intonation is now ok and there's not too much fretbuzz. The extra pickup on the blend seems to work wonderfully, dialling it in shifts from the brittle Tele twang to a much warmer sound. All 3 pickups running together sounds huge. The extra pickup really moves the sound to a humbucker rather than the strat out of phase thing, especially on the bridge pickup. When I have the middle pickup on its own it seems quite bassy, which really helps the sound but doesn't sound super on its own.
Anyhow, happy with it. I'll finish it off next weekend and get a sound sample so you can hear what it sounds like in the different positions, I'll apologise for the playing now...