Thanks to all of you for the many replies. As well as the replies to this thread I've had emails from several of you, wishing Tom the best of luck, and I feel quite overwhelmed. You have all been so very kind. Thank you, so very much.
First, a quick update on how we are all getting on. Tom is still ridiculously cool about the whole thing. I'm so proud of him. He knows it's going to be difficult at best and painful, and he's so pragmatic about it all. He's about to start a procedure that will take at least a year to complete, perhaps two, and he just shrugs his shoulders and gets on with it. Bless him.
Here's what things are like for us. Today, in all the sunshine, we put up the boys' trampoline and Tom got in lots of bouncing--he's not going to be able to go on it for a year, after next Thursday, so he's really making the most of it. Then he spotted a sheep in the pond about 500 yards away, and so we raced over and dragged it out (it took me and the two boys and Tom's rope to get it out) and we did some elementary CPR on the sheep, which probably didn't need anything other than rest, but still...). Then we came in and ate pizza, and now we're eating the last of last year's apples from Grandad, and watching the Simpsons.
As you can imagine, it's boy-heaven here, with or without foot-frames and Maine Coons, I just want it to be even better. As a veteran of animal rescue of all sorts, I can't imagine buying a cat from a breeder. It feels immoral to me. I'd feel dirty if I did it. Even if it meant making Tom happy. For Tom's sake I almost wish I felt different, but I don't. Meanwhile, there's no shortage of pedigree cats available: I have a friend who runs a pedigree rescue, and she's got british blue kittens, youngish bengal cats, and all sorts of siamese and oriental cats available (let me know if anyone fancies helping out with any of those!). It's just the right Maine Coon that is in short supply.
Tish the Maine Coon looks gorgeous but she's apparently suited only to a home as a single cat, and we have four all ready. Bums. I'll contact the rescue and see what they think but I suspect it's unlikely. Meanwhile, give me a shout if you hear of anything else around. I'd love to know. As would Thomas. And thanks again for your help and support. It's amazed me, and meant more than you can possibly know.