Thanks everyone.
GOOD NEWS!!!! Sam saw the vet last night, who couldnt find any sign of a tumour, his mouth is incredibly red and inflamed, but he is confident it is just 'calici mouth' - although said not to give him antibiotics, which sounds odd to me!! Overall, the vet is very happy with him, he has put weight on, his heart rate is normal, his heart murmur isn't overly worrying. He wants to keep him on the same dose of medication, rather than increasing it, and see him again in a month for more bloods - there is a chance that as his mouth was so bad on Fri that his thyroid levels weren't accurate, as the calici could have suppressed it. HE isn't pushing for the op at the moment, as he has never been overly hyper-t, and his weight has always been relatively stable - still not convinced, but that is something for a different time. HE wasn't overly concerned about his liver values either, although until his thyroid levels are down more, we wont know if they are causing the liver issues, or he has a slight underlying liver problem. Oh, and he has earmites too!!
I was soo relieved, I had really been dreading going to the vets last night, but soo glad I did.