1] Do not pick a short course, even if there is not the option of doing the full course, don't bother wasting your time on it, it is not considered by any universities [for medicine].
2] Do not do any OCR nationals, again, it is not considered by any universities. Distinctions do not equate to A*/A's.
3] Do not do GCSE further maths if you have already done GCSE maths, only one will be considered.
4] Pick subjects which you can get A*'s in.
5] If you have a double science award already [e.g. A*A*] and considering doing triple science, only do this if you know you can get at least A*A*A. Otherwise you'll be losing precious A*'s.
6] English language is very important, so prioritise this if need be, in order to get that A or A*.
You want to be aiming for 6+ A*'s in order to be a competitive applicant, so don't waste your time on subjects or qualifications that are not considered.
Peace.