It really depends on what University course you want to do afterwards, and at which University.
For some degree courses, Universities actually prefer mature students to have studied for the Access course, as it covers Academic Skills such as researching, referencing, computing, portfolio building and time management amongst others. A Levels, on the other hand, although the same level academically, do not offer the opportunity to learn the 'skills' necessary for undergraduate study. Most Access courses will also cover English and Maths at GCSE level, so separate GCSES will not usually be necessary.
However, other Universities prefer more traditional qualifications, and will give preference to those with GCSEs and A Levels. My advice would be to contact the Universities you are interested in attending, and finding out what route they would recommend before you commit yourself to anything.
Hope that helps. Good luck with your studies!