If you want to apply for cambridge, go for it. Your a-level grades are amazing. As long as you apply to 4 other schools you would be happy to go to, with at least 1 or 2 you think you will almost definitely be accepted into, there's absolutely no harm in applying to cambridge. Do bear in mind though, your PS needs to be strong. Generally, Cambridge says that at least 80% of it should be about activities directly related to the degree you apply for.