Age doesn't matter. Speaking of Access to Medicine courses, I would recommend the College of West Anglia. In my class of 2021/2022, all of us scored 45 distinctions and 15 non graded passes.
Teachers at the College of West Anglia, want you to do well, from the sense of satisfaction it gives them and the College's reputation.
All exams are vetted by an external member of the exam board to ensure the teachers are not being too generous with the marking. Relocating, if you earn under £30,000 the College can contribute up to £450 to your rent during term time. 8/9 got into medical schools such: Edinburgh, Kent and Medway, Brighton and Sussex, Exeter, Liverpool, Lancaster and Cambridge.
As for GCSE's, I did mine as a private candidate, so I learned at my own pace. I retook seven, English Language, English Literature, Chemistry, Biology, Physics, Spanish and Maths.
I am entering my second gap year and am going on 28, born in 1995.