THe older/traditionally good ones are normally the best. People's opinions very massively.
Dunno why loads of people are hyping up Nottingham it's just a standard middle class uni, same as Exeter.
Warwick is world class for Econ, but not much of a reputation for the humanities, and is relatively new as far as prestiege goes.
Oxford and Cambridge are good - and are famous for giving undergrad students a world class education.
But many of their professors, a majority actually, didn't do their undergrads at Oxford or Cambridge etc etc.
Just look at the Russel Group and you've got your answer there. If you want more, look at companies in the field you want to work with, look at the 'our people' section, and look at the unis the high up people on there went to. You should be able to get a pretty good idea from that.
Also should be considering what is a good uni for you - there isn't much point going to Cambridge if you don't think you can get a 2.1 there (employment wise).