In a nut shell going back to college will in no way hold you back or be held against you.
Unfortunatly the odds are always going to be against you in becomming an RAF Pilot. ie a shrinking air force, less aircraft equals less opportunities. Also still lots of young bright kids still out there still competing for those slots. Additionally selection tough, training long and tough.
That said still one of the best jobs in the world for a young single guy and if you dont try then you will probably always wonder.