If you really want to do it, or ask for feedback as to why you got rejected, I think it'd be better to get someone from your school (tutor or something) to ring them up. There's no harm in asking for clarification and possible reconsideration, although they seem to be pretty firm on their decisions (not to mention that they are unlikely to say yes, cause otherwise they would have to reconsider every single application that was unsuccessful).
But if you want to go through with it, you should be completely confident in your abilities as a student, cause if you succeed in getting an interview and end up being not so brilliant it might work against you much more than if you had an interview offer straight away and/or should you decide to re-apply (assuming you want to, of course).