Living in Surrey is expensive. Cost of normal food and drink isn't that different from elsewhere, but going out you'll be paying nearly London rates.
Housing is the single biggest factor. Room costs on campus are very high for not very much but, to be honest, they are at most universities around the country. If your parents are able to pay, they probably will, because that's the price of seeing you in a protected environment for your first year. But it's the south-east, and rent off-campus is also extreme. A small room - and there's not much else in these parts - is likely to be £550 a month. You are in the same boat as Guildford's long-term residents.
Having said that, unless you are really, scrapingly hard up, you are best off making your decision on the quality of the university and dealing with the cost of living, which is always hard, when you get there. There are ways and means to deal with these things. Surrey is rightly considered an excellent university and has excellent facilities and you'd do well to go there if it's got a good rep in your subject.