Usually access to medicine courses don't accept school leavers directly and often require students be at least a couple years removed from school. As they're not really designed as a "resit" option for school leavers who didn't get the grades initially (although they may be suitable for such a school leaver who then left school and worked in the healthcare sector for a few years as an HCA or something). Some might not have an issue with that but you'd need to check with them.
Also bear in mind not all access to medicine courses are accepted by all medical schools, so you would need to check if any individual course that would accept you as a school leaver would also be accepted by any medical schools you wish to apply to.
In your situation your best bet would be to just make arrangements to resit your A-levels, as it would be quicker and more straightforward (particularly if you already completed and passed the science endorsement in your science subjects, as then you just need to look at retaking the exams themselves)