Thanks to Cairndon I am now the proud possessor of a packet of ten much more business-like tent pegs, so I can peg the corners of the tent, then if need be add the guy ropes without having to scavenge the pegs from the tent itself. Also of a couple of 4-metre lengths of cord to use as guy ropes, long enough to double right round and tie tightly - the existing lengths will probably do the other two sides if I tie them together in pairs.
It depends a bit on where I find myself. Ground soft enough to take tent pegs isn't available in every car parking place. But I'll take it anyway, and see if the occasion arises.
Every time I look at the weather forecast it's different. No sooner have I though of a plan that would work than it changes and the plan looks poor. But this is all a week away. I'll just pack everything then see how things are when we get to it.