Update
On visiting the vets today, she checked inside his mouth and as I feared, food is building up in his mouth again and the vet is concerned. He also still has diarrhoea. Vet said that this is showing that he is getting something going through his gut but not enough. Yesterday he weighed 1.6 ounces and today he is 1.4 ounces.
During the GA the vet assures me that there was no obstruction to stop him from swallowing, no signs of oral thrush and other than a sharp tooth that was filed, his teeth look in good condition and he is able to move his jaw freely.
When feeling his belly, Graham made some very quiet squeaking noises, which she said she didn't like the sound of.
The vet has now suggested taking him back tomorrow morning for an x-ray so that she can look at what is going on inside him to hopefully rule out anything sinister, like a tumour.
I've made an appointment for 10am tomorrow and we have left it with the "We'll decide what to do next once we have seen the x-ray results, but it's not fair to Graham for him to continue like this". I am to continue with the ranitidine and critical care, along with another dose of metacam in the morning.
Feeling very sad. Can't bare the thought of my little Graham Groos being so poorly, and possibly in pain. Will be crying with a large glass of vino tonight :-(