Identify the course you want to do, then identify the universities that offer it. If it is not clear on their website what they accept, email that admissions department for some guidance. If I recall, there ARE universities that allow entry with Access to HE (for some reason Bristol rings a bell but i'm too lazy to check). The issue you have with science-based courses is that a universities view is that the Access course does not give you a good enough base-knowledge to be able to succeed. You can self-teach A-Levels at home. It's more difficult but certainly doable. There also is the option of Foundation years, however, I would try to avoid them if possible.