Accept a place at a University that has given you an offer.
Then bide you time, wait it out, and see how your results go.
If you get AAA, I would definitely suggest taking a year out and reapplying. You can ring up the Uni and say "Thanks, but no thanks." I'm sure.
With AAA, you have a decent shot at Uni's like UCL, KCL, Durham... even Oxbridge, if you feel like it.
If you get AAB, seriously think about whether or not you'll be happy at whichever Uni you've Firmed. If you feel you'd be better at Leeds/Sheffield, then JUST TAKE A YEAR OUT. Do it. Travel, earn some money, get some work experience, do some CV-embellishing voluntary work. You won't regret taking a gap year, whereas you might regret being too chicken to actually do it!