No, of course don't aim way above anywhere you're likely to get in. Aim at universities roughly of your level, maybe some higher and some lower. Do remember that you don't have to start applying until you've got your AS grades back - wait and see how they go first. And don't forget - just because the university isn't massively prestigious, doesn't mean you won't enjoy the course! The vast majority of students end up loving their uni wherever they end up; most people in my school thought they wouldn't be satisfied unless at Cambridge or Oxford, and most didn't get in but then went on to prove themselves wrong.