There isn't that much to learn for A levels, 5 months is a long time and if you put your nose to the grind-wheel and do all the past papers then yes, this is achievable.
However - you will fail the pre-clinical exams at many med schools (particularly those with an exam-intensive divide between pre-clinical academia and the clinical years) if you adopt this approach. I recall working out that in a 1 hour lecture (in essence the A level biology catch up lecture) we covered what took 8 biology lessons. The pace did not let up with subsequent lectures on completely new material. Our first serious exams to cover 3 heavy science modules were 4 months in after the Christmas break. There are no past papers to practice, there are no "typical questions" to learn by rote. Only more material than you have ever had to learn before and it is easy to fall hopelessly behind. (Though you only have to pass eg: 50% rather than excel eg: 80-90% like at A level).