Hi there, vet Andrew here. I see you're offline so I'll leave this as a message for you.
It sounds like Chuckles may have a respiratory tract infection such as equine flu. Horses can get a mild case of this even if they're up to date with their jabs. The fact that he's eating is a good sign, but the temperature is not - I'm assuming his temp is above 38 C. He'll most likely need antibiotics, and possibly anti-inflammatories and a drug to open up the airways. In view of the high temperature I'd phone up your vet first thing in the morning and arrange a visit.
In the meantime, you need to make sure he can breathe easily by ensuring the stable is well ventilated, and only give him soaked hay to eat to minimise dust. Spray a little water on his bedding if you think it's dusty.
If you have other horses or ponies, try to stop him having direct contact with them, and tend his stable last to minimise the risk of infecting the others. Wash your hands if you touch him or his equipment.
That's all you can do until the vet arrives, but try to check him again once more tonight, and keep your vet's number handy in case he goes downhill. I think that's unlikely given his appetite. There are other diseases such as Strangles (infected throat glands) which can really do the rounds at certain times of year, and can be quite serious. I hope this helps, and wish you all the best. Vet Andrew.
Hi there, vet Andrew here. I see this question is still active, and I haven't had a reply from you which is worrying. How are you getting on?