Quick update. He's looking OK. I can't say happy, cat's aren't meant to be kept in a cage, but comfortable. He's eating well - ate all his breakfast and demanded more so some extra was delivered. Little worried that we won't be able to get him out of there if he keeps eating at this rate!
The surgery looks very good - when our cat Niblet lost an eye it wasn't as neat but she was injured so they were sorting out a mess rather than from the ideal starting point.
I didn't get a photo yet but I will. I'll spare you a close up - you may be as squeamish as I am!