Oh, it's not disappointing, just feels weird! An anticlimax, as I said. Doesn't feel like much point telling people if it might not happen. He's finding it odd too - getting well dones etc from his friends and he can't quite get his head round why people look at an Oxbridge offer so differently from his other offers.
And no, I don't think he's spent enough time there (has been to an open day, with his sister, after a bit of persuasion, and then obviously to his interview - this is where I think the Oxford system is way superior, lets you get a much better feel for the place). I've suggested he makes a term time trip to see what it's like full of students. I don't know if his college do an offer holder day - dd1's Oxford college do (I think at least partly because it's one that quite a lot of people end up at having chosen a different one), but I don't think that's common.
His other choice is Manchester, same offer as Cam, for an integrated masters, and he just loved it there, felt immediately at home, etc. The dept is big and busy and buzzy, and he could clearly just see himself there.