Well, I haven't read the advice of most tyre manufacturers, the rim was freezing cold as it came in from the garage, the tyres had actually been pretty close to my radiator, and as it happened, despite how terrible the video apparently is, using zip ties made it much, much easier to fit the tyre.
Also, after some experimenting, I found that doing the valve first was easiest. When I did valve last I couldn't manage to do it without pinching the tyre. So I did valve first, loosened off the nut on the valve so that the tube could drop down into the tyre, and it worked really well.
This morning I rode into work on the tyres. I needed a little more effort to get going on them (understandably — they weigh more and aren't slick like my old tyres), and made an odd noise — a bit like riding on wet grit, or, when I'd got up to speed, like I had an electric bike. But passing pedestrians didn't seem to notice, so they're probably not too noisy. And they didn't affect how long I took to get to work. Now I just need some ice to ride on.
Valve area last gives you more tyre to play with, so maybe you were just unlucky with a tube pinch. Not sure how you guys manage that though, not something that never occurs amongst our circle, maybe it is an age thing. Something like over 50 and it does not happen, maybe down to luck maybe something else.