I've come back out of hiding. The cat started to perk up about 5 minutes before we were due to leave for the appointment with the vet and by the time we got there he was ready, claws drawn.
She couldn't find much wrong with him except for a raised temperature and came to the conclusion that he was 'under the weather'. So he had an injection and we've got to go back tomorrow.
It's my turn now to cover my eyes and someone else can go and hide!