Just an update: I tried several pairs of walking shoes in wide fittings over the space of a couple of months including a £200 pair of which one shoe was a perfect fit and really felt good, but the other wasn't.
I eventually went to a local(ish) shop and tried a pair which seemed OK , they were only £50, looked a lot like a trainer but were waterproof, breathable etc etc and seemed to fit. I could return them if they weren't right so long as they'd not been worn outdoors.
I tried them on again at home and they seemed OK still, but after about ten minutes my feet felt hot, in fact not just hot, they felt as though they were actually burning. (This was while my wife was in hospital (Feb 2 - May 16), and life was complicated). I took them off and they've sat there unused ever since.
With the weather turning colder I tried them outside yesterday (probably no chance of returning them now anyway) and they were fine.
One day it will all be firewood.