GB68c,
Tricky situation. I just graduated from Nottingham this summer and although i might therefore be a bit biased, i'd say stay on and finish what you've started. I didn't enjoy my first year that much, my degree was a tad boring, but things got better in the last two, when you get your own house with your mates (don't know if you are doing this, but i recommend it) and you get more freedom to choose what modules you take in your degree programme. Nottingham has a UAS and a gliding club that I joined, try join one or the other if you haven't already done so.
As Gin Slinger says, Oxford will still be there in two years. There may even be more avenues for some form of sponsorship opening up then (I'm optomistic by nature). Nottingham is a good uni and the degree you obtain will be worth something to potential employers. All the advice on this forum from the professionals for us wannabes is to have a backup plan. And a good degree is a very good backup plan. There will be others who may say go to Oxford now, and i can understand your temptation to quit uni now that you have the opportunity to enter training in your hands.
Anyway, just my humble opinion. I feel better entering training with a degree to fall back on as I'm quickly learning that the only certainty in our chosen career is that absolutely nothing is certain. Whicheverway you choose to go mate, all the best.
And don't forget that university will prepare you well for one aspect of wannebeship - being heavily in debt!
Good Luck
