I think this may be a waste of your time. Top unis would still accept you as you have a really strong set of GCSEs. Most of the time they do not look that much into your GCSEs unless they are related to your course. Even if you applied to business studies at a university they would look at your maths grades, english grades and maybe ask for 5 subjects that are graded 6 and above (at a good university). I would not worry about it i know people who got a 3 at gcse business studies and are now applying for management. Instead i would focus your efforts onto studying for your A levels and applying for something that would really make you stand out. You could do an EPQ (good for getting a lower offer), apply for sutton trust (thats really good for top unis my bf got an offer from exeter for comp sci of AA bc of this), do a programme for a uni you would like to apply for (i did discover bath and got an A and now have an alternative offer as well as something for my personal statement- was only a few weeks as well). There are other programmes like realising opportunities that you can apply for and just general work experience. Just look around they really make you stand out bc no one else can be bothered and you only have do one or two to make yourself stand out. However, in order to actually answer your question you would have to contact your sixth form/ college and ask if they do a retake for business; a lot of them dont and only offer English and Maths. You can pay money to have a retake but you would have to get a school to let you do it and it is quite a hassle. Honestly i am applying for university now and many people have already applied and anyone who did these things got amazing offers at amazing unis like St Andrews in some cases despite not meeting the grade requirements. I am applying for a german course w a grade 4 in german and i contacted universities who just did not care that much and said it would not be an issue. Sorry for such a long answer hope this helps.