You can only be a Pilot in the RAF if you're an Officer. NO non-commissioned aircrew fly aircraft.
So, if you want to be a Pilot, and fly planes, you're going to have to be an Officer.
If you want to be a Pilot Officer, you're going to have to impress the board that you are serious about being an Officer in the RAF, and everything this entails. After you have convinced them of your wish to be an Officer, you should explain why you want to be a Pilot.
If you walk into any AFCO or OASC interview and tell them that you're only bothered about being a Pilot, and you're not bothered about much else, I guarantee that you'll get to part 1 in selection, and no further.
You should definitely try for Direct Entry, but don't rule out university. Degrees are a good back-up if things don't work-out with the RAF.