After lots of time spent with spray cans and sandpaper, I've finally got a nice finish. I stuck with polyurethane varnish, and I'm quite happy with the gloss, and it should be pretty tough.
I've glued the neck in. Quite scary in concept, but in practice it was really easy. Everything lined up perfectly straight out of the box! I used my ancient drill press to push the bridge inserts in, then I used fine cotton thread to make final checks of alignment. The kit was spot on, perfect, and just needed glue and clamping together. I've fitted all the fiddly bits, lined up and fitted the pickups, and all the pots and wiring. Putting the pots in is really awkward and caused several expletives to be expressed at a volume my amp can't reach! I've still got to string it, but I will wait another day until the glue is properly hard, and once strung, I'll post some photos.