I don't really believe anyone can be completely confident in getting an offer, because it is competitive, and some very good applicants do get rejected because there are just too many people. The extent of this partly depends on which course you apply for.
As I said before in a recent thread, it's a case of balancing up the risk (Are you going to sacrifice a safer backup option by applying?), and writing the best personal statement that you can manage. If you are confident that you can be the kind of applicant they would want to make an offer to, and applying isn't too much of a risk, then I would encourage you to apply.