Joe,
All of the above is great advice and in many respects I agree but I have to say I'm going to throw a couple of other ideas into the pot.
Firstly, is it the RAF you want to join or would you enjoy flying with the other services. There are plenty of threads about the differences between the services, but crucially the Royal Navy accepts Aircrew (you go through as a joint pilot/observer candidate and they offer one or the other) up to the age of 26 and I believe the Army Air Corps. set their age limit about the same.
Secondly, how much would you owe at the end of your degree? Just a thought as for many this can be a deciding factor because it can make chasing civil aviation that bit harder if the forces don't accept them and they have huge debts.
Obs cop