Thanks Mary. Looking forward to seeing Molly if you get a pic - and I'm very glad to hear she's doing so well! I'm not really frightened, that's not quite the right word. I'm not sure how to describe how I feel - except tired! I do know I am really annoyed. Poor Silvie has been dealt such a rubbish hand - arthritis with Metacam for the rest of her life already, and now this - and she's only 8! She deserves so much better. But they all do, don't they!
And Mark - I had read those things about the Iodine as well. The Glasgow University site which Tan has posted on the info page says they keep them in for 4 weeks! I would really struggle with that, but I'd be happy to do it for her. I will definitely enquire about it.
Will let you know how I get on at the vet tomorrow. Thanks for the reassurance.
Edit - Weds pm
Been to the vets this morning and feel a bit more relaxed after speaking to them. They offered me the three options - tablets, surgery or Iodine. I have emailed PetPlan to see if they will cover the Iodine treatment for me as I'm quite attracted by that. It will mean no invasive surgery, much less risk of side effects or infections, no anaesthetic, no need to do it again (surgery only usually removes one thyroid gland and the condition can then later affect the other one, I've read) and various other benefits over surgery. The only drawbacks of it are the cost, and that being becasue the cat needs to be kept in hospital isolation for at least two weeks after the treatment - becasue they're radioactive! Silvie and I will hate the isolation part, she'll adapt OK and I'll struggle! But if it means she gets the best tretament, then I'm all for it and I'll find a way to cope. The guinea pigs will get lots of extra hugs!
I'll let you know what I find out and the route I decide to take.