You don't just pick a university because of the name and its reputation, you pick it because it offers the course that interests you the most and thats the important thing, the simple thing is while Oxford and Cambridge are the best universities in the UK they are not the best in every single subject.
You also have to look at what you want to take away from university and the location, I'm used to living by the sea and for me I would hate to be somewhere like London and be miles away from the seaside and countryside but then I wouldn't like to be completely isolated either. So fair enough you now regret your choice but at the time you should have picked the university that felt right for you, if you're university is the best in the subject that you want to go on to pursue as a career thats whats going to matter to employers that and how well you present yourself.