If you aren't that bothered about university life (it isn't ALL boozing and wasting cash) then you can always consider an Open University degree whilst in the RAF. However some guys coming out the other end at 38ish have regretted missing out on that opportunity that a degree presents, so it is really 6 of one and half a dozen of the other.
If you are going to reapply after A-Levels, what are you going to be doing - you don't want to be mincing about and if rejected never end up with a decent job. Perhaps go to uni and leave if accepted, and if repected go to UAS for the remaining time at uni (allowing time to settle into uni before embarking on UAS commitments)?