Why would you only apply for 2 medical schools, if you are going to apply go full out not half-hearted. Medicine is competitive as it is, restricting your options even more is just wasting an application. I would recommend you apply with a levels in hand because with your grades you are not going to get any interviews for medicine. As for keeping a back up option you have a 5th option just for that, and for computer science I cant imagine they would accept your personal statement as it is orientated around medicine. Applying to medicine after you have done a different degree is much more competitive, if medicine is your goal consider strongly how you are going to approach this, you still have time to recover smash your a levels and you will have a chance. Good luck.