The most important part to joining the RAF which no-one has yet mentioned is that above all else the RAF want their potentail pilots to be an Officer first, pilot second. You must select a ground branch as a second and third option if you want the RAF to take you seriously..... and you should be committed to those ground branches should you not make it as a pilot.
The RAF doesn't want pilots. It wants OFFICERS who can be pilots.
There was an excellent book written in the late eighties about the whole process of applying to the RAF all the way through to joining a front line squadron. Only problem is I can't remember who wrote it or what it was called. If you can find this book it will still be as valid today as it was then.