We went back to the vet on Wednesday evening and she injected him with an antibiotic and a long-acting painkiller, and took bloods. We discussed admitting him but she felt as he was well hydrated (and she gave him 150ml saline while we were there) there wasn't really much else they could do and felt he'd be comfier at home. The bloods they could analyse on-site were clear and the rest had to be sent away. We discussed how difficult it is for me to get pills into him - he is much more cooperative for the vets than he is for me - so she suggested they teach me how to inject him. We agreed that if he was still as poorly I would take him first thing next morning without an appointment, but if he was doing better, I'd take him in in the evening, and I brought him home. Oh, and they weighed him, and despite having eaten very little for 4 days and nothing at all for 2, he'd gained 40 grams.
He was so poorly on Wednesday evening, not eating, leaking tiny amounts of liquid poo from his bum, crouching on the floor in the hall all night, and I really wondered if I should have asked them to admit him. I didn't sleep very well and got up to check on him at midnight when he was obviously much better and asking for some food. He's gone right off poached chicken; I assume he associates it with feeling ill, so I gave him some wet food which he gobbled and some more at 4am and breakfast time. I went to work but couldn't really settle and they let me work from home in the afternoon so I could keep an eye on him.
We went back to the vet Thursday and they taught me how to inject him, confirmed all his bloods had come back as normal, and they gave me 4 syringes drawn up with his antibiotics. He ate normally on Friday and his injection went fine. Yesterday he slept all day and didn't even ask for his tea. I made a hash of his injection, squirted antibiotic all over his fur instead of his insides so had to use tonight's dose, so he'll be a dose short. (Rang the emergency vet to see if they would give/sell me one but they'd have to see him first and having paid £350 in vet fees in the last week, that's not an option). He has a blocked nose now, poor thing, and is very sleepy and snuffly. He keeps huffing through his nose and looking confused. I put him in his carrier earlier with a bowl of boiling water next to him and a towel over it all to give him some steam inhalation. He hated it, but it did seem to help.
So that's where we're at. If he's still as snuffly tomorrow I might have to think about the emergency vet but fingers crossed it'll settle.