Not much really. Low level admin work assuming you got C or above in English and maths GCSEs. Sometimes there are in house promotional prospects with that sort of work if you can impress. It would strengthen it tremendously if you did an A-level alongside, including if that meant doing National Diploma (size equivalent to 2 A-levels) instead of Extended National Diploma (equivalent to 3.) If your school or college doesn't offer that you might consider adding an A-level via distance learning, which would have a cost from around £350 and upwards, depending on the provider, service level, and payment plan. Your school or college would almost certainly be happy to act as the exam centre. Maths or a language might be particularly helpful, but any relatively traditional A-level will help.
You might also look at other vocational qualifications, that are more directional in terms of career than business. You need to think about what you enjoy, and what you might want to do in future.