Thanks for the encouragement, Steve.
I got the decals on yesterday, then the varnish last night and this morning, so ... she's finished! What I said about further drama was appropriate, as it happened. I now understand what people mean when they talk about poor-quality decals - these ones went on, but they tried their damnedest to fall off again. I think I'd recommend getting some alternative ones if you're thinking of building this kit. They did not succeed in falling off, however, and none of them broke up, so it all turned out OK in the end. I've also ended up with a pretty rubbishy finish thanks to the varnish not drying evenly. I think this is my fault - should have thinned it more - so I'll take that one on the chin and do a better job next time.
What we have ended up with, however, is a Mosquito. A slightly twisted, streaky Mosquito with one knackered undercarriage leg, but a Mosquito nonetheless ... and I love it. I've really enjoyed the build, in spite of all its trials, and I've learnt a few things, so that's a success for me. The Mossie is currently on the windowsill in front of me, so I can enjoy looking at it in what's left of the daylight before I put it in the display cabinet later. Here are a few pictures of the finished product.