Ok, so eventually I decided to sand the neck join (is it called the heel?) on the flat back surface (opposite side to the fret board). I didn’t think I would be good enough to match up the curved surfaces on the other side...I don’t even want to think about it. Neck and body fit hand in glove now. Hopefully not too much effect on things later on. Back of the body sanded. Stopped there as the kids are driving everyone bat guano crazy. One step closer.