Basically, after that rather long-winded explaination (sorry!) I was wondering if not having stuck with Air Cadets will be a major drawback in terms of AFCO and OASC interviews?
Not at all. You don't have to mention the ATC, but if you do, don't be negative about it.
Secondly, I don't do much in the way of team sports - I enjoy kayaking and mountain biking, but not really anything on a playing field. I'm starting my Silver DofE soon and hoping to do my Gold next year, but besides that what should I be doing to get a proverbial tick in the proverbial 'Teamwork' and 'Leadership' boxes.
A good start, and bear in mind the the service element may introduce you to an activity/group that you can develop further, which you'll need for Gold anyway.
I was considering getting a holiday job for a month or so in the summer at one of those outdoor pursuit places for kids. Is that a good idea?
A good start, but think along RC's lines and see if there's something you can start/build-up along the team/sport lines.
RC - please use either a dictionary or a spell-checker, or use Sgt.
I'd suggest taking a twin-track approach as far as the RAF and university are concerned. You can apply for a university bursary worth £1500 a year, once you have a place at university. A degree is good insurance if you don't get in/get chopped/get a medical issue or just hate it.