Sorry, just realised I hadn't posted an update in a few days.
Widget came home on Saturday. I've got to take him back in a week for a check up but he's doing ok. He's on a special diet for now and he's pee'd normally a couple of times that we've seen. He's got some more cystaid to take for a while. He's very bright in himself and wants lots of fuss and cuddles.
The main problem we had was Pixel. She freaked out when we got him home (presumably because she couldn't identify him by smell) and went absolutely nuts. She screamed so much that she gave herself a sore throat! She would start screaming as soon as he even meowed- even though he was in a different room. We separated them Saturday and Sunday. On Sunday I went out as soon as the shops opened and got two feliway defusers. Fortunately they made a big difference. She's still hissing and spitting and occassionally yowling but she's so much better than she was. In fact, they're currently sleeping in the same room... which wouldn't have happened Saturday or Sunday. She's a right grouch with him though and won't let him pass (or gets very funny about it when he dares to dart past her). He's mostly indifferent- just a bit wary. I think he's more confused than anything.
However, other than that hiccup, he's fine and doing well so far.