bit of a vague question
obviously the higher ranked universities are a boost to any job application you make, more so for certain jobs, but a tryhard with a 1st from oxbridge will always get turned down in favour of a normal applicant from an average university who can interview well and get themselves a little job experience if the oxbridge grad can't stand up in an interview
what im saying is its far from make or break
spend your time at university wisely. get some kind of job experience under your belt and you'll be fine