Hi JOF01
Firstly, possibly before some of the less tolerant members of PPrune get on here, good luck with what you do.
You mention that you have always wanted to be a Pilot, but that you are happy to accept another role as Aircrew. Everything you need to help you prepare is at the sticky at the top of this forum. There are some excellent tips etc.
I would encourage you, based on your dreams, to concentrate on getting your grades up to the standard required. This would also give you time to improve on your fitness. Once you have done this, apply in the usual way. This would only postpone University for a year. After a year, you can apply to Uni and also apply for pilot/WSOp at the same time.
I can assure you that, should you be successful with your dreams, you will have a lifestyle and career of which others can only dream. Yes the RAF is not what it was, but with new/relatively new and future aircraft types the future is exciting.