Should I do a GCSE or A Level?
A levels and GCSEs are traditionally offered to school age students but it may be possible to take a part time course with a local college or online provider. It's likely that you would need to pay for your course but if you are taking a GCSE in maths or English it may be free as part of one of the specific courses above such as the Access to Higher Education course.
Doing a part time GCSE or A level can be a good starting point to dip your toe into academic studies and contribute towards specific entry requirements needed for the future.
If you are going to use an online provider, be sure to check out its credentials by making sure there is plenty of support and that their qualifications are through a recognised UK awarding body such as Edexcel, AQA, or OCR.
One example of of an online provider for A levels is the Oxford Learning College.