Can I enter clearing if I still get into my back up uni?

Well the title is pretty self explainatory, basically the uni I have firmed has a grade requirement of A*AA, I got ACCC in my AS levels and I geniunely cannot gauge how well i have done in my final exams, I think they went well but you can never tell with these things. My insurance uni is one in London, which at the time of confirming my choices wasn't a problem, however my financial situation has changed in the past few months and I don't think I could sustain living there even with a maintainance loan. I was just wondering if I don't get into my top choice do I have to stick to my back up or can I enter into clearing anyway and try to get into a uni in an area which is more sustainable to live in