Bristol is a big place, frumpy so I think there's room for all types. Rather than asking what it is thats worrying your son, let me tell you about my son and his friends and then he can see that there are all types there?
My DS was at an independent day school and is pretty clever but only really works when he has to. Before uni he had never been out clubbing but preferred Xbox games and films. He had lots of good friedns but felt confident to strike out alone - one of his closest friends also went to bristol but they only met up once in the first week and seldom since then, so was happy to make new friends.
He lived in a catered hall with long corridors last year - Hiatt Baker, the biggest - which I thought was grotty but which he loved because of the corridor style of living: a run of about 20 rooms to one kitchenette and everyone just left their doors open if they were in the mood for company and closed them if they were not.
I can honestly say I dont know of his group of 12 or so regular friends how many were at private school, how many applied to Oxbridge and didnt get in or anything like that - its just irrelevant to them.
the friends are from all over the country - Manchester, Newcastle, Epsom are the few that come to mind. And they are all subjects - a few other physicists but also history, music, geography.
They did alot of growing up in that first year and rather too much clubbing for my liking but my DS also joined a sports club and did some social sport based around the hall of residence. The physics dept also has its own 'club' with group get togethers and sports meetings. So even if you find you dont get on with your corridor mates, there are lots of other ways to have a social life.
DS's friends seem to be hard workers - he's in a house with a few others this year and they do have problem solving sessions between themselves (the physics group) and he'll often say that 'such and such didnt go out because he was working'. So maybe that indiactes a strong work ethic at the uni overall?
Have you been for a visit yet? I'd encourage you to do so, it'll give you a good idea of the place. And do go up to the residences on the downs where most 1st years live to get a feel of there, too.
Anything else in particular, that might help, frumpy?
And I know exactly how your DD's friend feels, webwiz - when DD got her Bristol rejection a couple of weeks back she was inconsolable for several days. It was of some comfort to get an email sying they'd had 1300 applicants for 70 places - it is such a tough year.