Gentlemen, thank you all for your kind words of commiseration.
In retrospect, perhaps it was lucky it happened when it did, as it has turned out easy enough to rectify. If it had happened after decaling and weathering, it would have been a much bigger problem, and if I had to reorder decals, at this stage, could have knocked me out of the build.
Terry, Thank you for your varnish solution (no pun intended). It's not something I was aware of, but I'll bear it in mind for future use. I had assumed that I was at fault for not letting the first coat dry, but if it's a fault in the spray varnish, that's a bigger issue. I have been using the Humbrol Enamel Matt Aerosol spray up to now and indeed finished off my Bf 109 E, using it, without any problems. But this is something I'll be very wary of, in the future.
So here's where I am at the moment. Having given the wing surfaces a sanding I resprayed the RLM 75. When dry, I re-masked and sprayed the RLM 74. This is slightly different from my first attempt. as I am doing it by eye, rather than using precise measurements. I then redid the panel lines - these are getting shallower with the extra coats of paint and varnish. The masks were removed and a couple of coats of straight Klear were sprayed to protect the panel lines and to prepare the surface for the decals. The photos are of the revised paintwork.
If I'm happy with the surface, the next step is to start with the decals. I've also started masking the canopies, while waiting for the varnish to fully dry. As I'm intending to display the canopy open, this will probably mean masking them internally as well.
At this stage, most of the sub-assemblies are ready for attaching, so hopefully, I'm aiming to get this finished in the next week or so, barring no more disasters.