Many thanks for all your kind words, folks, and I'm amazed at the number of responses so soon.
There's some good advice in them, but above all it's clear that I shouldn't delay. I'm weaker than I was, while my weight dropped from 12.5st to 12st before my operation, and down to 11st after my stay in hospital. Any amount of eating since then won't shift it above that. But I'm pretty confident I can start off doing 3-4 mile walks with my poles without too much trouble.
it pays to be flexible and prepared to travel to try on and in a position to buy immediately whenever a suitable bargain opportunity presents itself.
Travel might be a problem as I'm not expecting to be driving again till maybe November, I'm dependent on my dear wife to take me anywhere. I have to say that because she's been driving me to and from hospital appointments as well as doing the Tesco shop on her own since May.
As for being in a position to buy immediately, I put £200 to one side for them in my bank account so long ago it has earned 17p interest! Overall I haven't been better off for years, because I've not been going anywhere or, the biggest saving, not buying petrol.