You have little chance of picking up a place post results day even if you get top grades unless you have previously been interviewed by the med school. PMS was one exception last year; some applicants who had previously been rejected without interview were called for belated interviews in late August, a number being offered places.
Should you find yourself with 4 rejections - and don't give up hope yet, you've still to hear from your final choice - follow Johnny C's advice. Work hard, get top grades and take a gap year! If you use it productively to boost your work experience and write a great PS, you stand every chance of getting in second time round - much cheaper and less risky than the GEP route.