The highest non-Oxbridge offer I have seen was 38 IB points. Yet for Imperial they're offering me 39 IB points for Computing (G400). UCL gave me a paltry 34.
For the record, 39 IB points is like getting 5 A's in A-level (atleast I think that is the UCAS tariff). I applied with my predicted 40, which means that I actually have to work in school now :/