Thanks for all the ideas.
He's not eating at all now. Had a couple of bits of chicken earlier and a tiny bit of Tuna........no interest in cat food or any more offers of Tuna. His breathing became a little faster.
Have opened a window, which has helped in the past and he's a bit better and falling asleep.
My vet has an emergency number, but that's as far is it goes.
Sorry i'm not replying in full. Hope you understand i'm all over the place.
We mixed his tablet with some cat milk when crushed and he drank some of it - he appears to be drinking.
Don't think he's going to make it