Thanks for all the ideas - I have managed to get him to eat some tinned
fish, and drink a little milk (I know about cat milk, thanks), and he's
looking a little better today, but still very listless.

I don't think it's stroke (mentioned this poss to the vet); his teeth
are OK, I think - the vet looked. Heart rate a little fast (might just
be 'vet-terror'); I have de-wormed him a couple of times in recent
months, so I don't think he has serious parasites; the vet carried out
std blood tests, and said that the values were 'uninteresting', meaning
not wildly odd. I'm assuming this included kidney and anemia tests -
certainly included liver and diabetes.

I appreciate the advice - thanks. Never thought I'd become this attached
to an animal (especially a grumpy one that scratches me - when in good
health!)

best
nick