Can you get the vet's records and have a quick court hearing or would your vet fax the records to them?
make sure they know he is a purebred, w/papers [even if he isn't]. find a cat at an online cattery that looks like him - then tell them that is his value, that he is a show cat [again - even if he isn't].
they don't care how much you love him - but they don't want to get sued for boatloads of money because something happened to a monetarily valuable animal in their care.
ask if you can visit him - that way you can brush him [as is necessary for a top-quality show animal - i mean it, be nice, but lay it on thick], do claw maintenance, etc. ask to be allowed to provide his food, as it's important that he keep his coat in top condition.
if they say they'll feed the food, again, tell them how much it costs [pick something REALLY expensive!] & that you'll be able to tell if he isn't fed it. remind them that since he'll need daily grooming, you'll be glad to feed him when you come to do that.
i'll be back in a minute w/some links.