Thanks Rick, Ernie, this has certainly been a trial!
I spent some more time this morning going over some of the edges to make absolutely sure they were flush, then mixed another batch of light blue and sprayed the fuselage again. I kept a little paint for touch ups...
There was still a faint trace of the primer edges on the rear fuselage so they were carefully sanded down with micromesh - basically just removing some of the paint I'd applied that morning to leave it level..then it was sprayed again..
Finally I'm happy with it! It's not perfect by any means, I just can't get to all of it, but fortunately those areas were not too bad so they don't show unless you get it in just the right (wrong?) light.
I've lost all the underwing structure that I so carefully drew on but that's a small price to pay...I'll just assume it represents the aircraft on a dull, overcast, winter's day: no sun = no translucence!

Now I'm going to leave it alone until tomorrow when I will start to mask off for the black stripes.
Thanks for looking in, and for all the suggestions and support!
Ian