Classics is a 4 year degree at Oxford and Cambridge. A friend of ours is reading classics at Oxford. It’s one of the few 4-year degrees, so count that into your budget.
Something to consider if money is driving your interest: If you have the academic credentials to be closely considered by Cambridge, then it is very possible that an excellent college (and by excellent I mean both rigorous and a good fit for you) outside of the “top 20” ranked schools will give you merit based aid. I have two nieces with great academic numbers who last year did not get into any of the “top 20” schools to which they applied and, as a consolation prize, they were offered enormous financial incentives from several of the colleges that had accepted them. Thus, they were able to chose based on fit; a variable I/we failed to adequately consider/research when my daughter applied to college the first go around.
As to fit, I would recommend disregarding food and accommodations as important issues when compared to finding a place you fit in culturally/socially/academically. As pointed out by several posters, attending university in England is a very different experience and those differences should not be overlooked in an effort to save a few bucks. If you can find the right place in the UK that would be fantastic - just try to make sure it is the right place - not just a place you got in.
Building on @Massmomm, language and sciences are 4 years - it’s only the non-language humanities that are 3 years at Oxbridge (don’t think that this applies to the OP, though).