The vet suggested a urine test, which might just indicate something that can be helped for a little while by steroids. I'm doubtful, but I'll take a jamjar of pee in tomorrow anyway. But the vet agreed that as long as Az wants walks and can stand on his own and walk up steps, he's got a quality of life that is more or less acceptable. As the vet said, it's not like this has happened suddenly, Az has had time to adjust to his more limited life. And he does still prance a little, and pull his cheeky face, and wag sometimes.
Maybe a few more weeks wobbling slowly around the hilltop?