Teva tape (£12 for 66 metres roll) came, and now installed. I was tempted to do a single round, but thought since the rear wheel is asymmetric - with spoke holes angled and larger, I'd go for a double wrap. I still needed to work the tyre slightly at lower pressure to get it to seat nicely - but only in one area & didn't need any soapy water. The 21mm width nicely fitted across the internal width of the rim, which was needed as the narrower thicker velox, which had a tendency to slip, had to cover the asymmetric positioned spoke holes, but also seemed to impede seating of the tyre...
edit. also improved my tyre fitting technique, so managed to fit both Pasela PT pretty easily using hands only.
edit2. probably still carry a tiny container of soapy water, and a toothbrush head, this winter, just in case...