A few simple parts bolted back in place and it looks like I've made huge strides in rebuilding this bike.
It now has its face back, at least for now, I suspect I'll need to take some of it back off to check the wiring when I can.
The bars are new, the old set, while perfectly servicable came off something else and the knurled sections didn't match the clamps so I bought these ones, they are pattern ones for a old BSA -A, B and M models, they are slightly pulled back than the other ones but look fine.

The wiring is getting complicated now as I try and figure out what connects where, I think this will be the hardest part to get right.