I didn't do as well as expected, took this year to retake and reapply, and it's worked out well for me. I applied for 5 courses, and had 5 offers (including from Birmingham, Liverpool and UWIC), so don't think that universities won't accept retakes! Taking the year to resit has been pretty useful, as I've been working (and saving!), and it's given me a chance to decide what I want to do.
However, think hard about where you'd re-do your exams. I just went back to school for actual exams, and studied at home before. This worked for History (went up to an A), but not so well for physics, so unless you can properly motivate yourself to study at home, it might be an idea to go to college to repeat the year?