Over a week later, the house seems empty. The signs were there with hindsight, he seemed to be licking and clearing his mouth more regularly, like he was in some discomfort, occasionally hacking really loudly.
I think we really did catch him just in time, I honestly wonder if a week or so later, he would have declined quite markedly.
He went to the vets with a wagging tail, eagerly sniffed around the carpark for other dogs smells, eagerly met other dogs in there, his last hours were very good ones for him, he was alert and eager. That's partly why we took the decision not to wake him up from sedation, strange as it seems.
It's fine, we did our best by him, life...and death carries on.
Thanks for the kind comments everyone ....