Finally I've tackled the power transformer wiring. It wasn't difficult, just fiddly. There's nothing massively complicated about cutting eight wires to length, stripping, tinning and soldering them to something else, but getting it to look neat, getting the twists in the right place, and generally not f'ing it up took a bit of concentration.
After all, if I fuck this up then something's going to go pop. Possibly me.