Got the plane out to create some shavings. I decided to do the neck pocket after all as it gave me a manageable sized chunk of wood to practice with. CA glue, as advised by all you knowledgeable chaps!
I've got a bit of final sanding to do to get the tops of the shavings absolutely flush, but the neck is nicely snug now.
Nut slot next; you can see in the first photo where the router slipped, then the fillet of shaving in place.
And now there's virtually no gap with the nut in place.
Again, a bit of final cleaning up to do.
Next up is slightly enlarging the neck screw holes on the body so the screws seat properly, then screw the neck on to confirm my suspicions, from just clamping the neck, that the bridge holes are in the wrong place. The holes certainly aren't on the centre line, (about 1mm north of the join in the body) and it looks like about 2-3mm too far forward, as Mark forecast!