You can pay for tuition and exams privately if you want to do an intensive one-year course. There are many private institutions in central London. I am doing an As with a private college. One exam costs £55 and the practical exam costs £300. You have to do compulsory classes before the practical exam.
If you are within the 16-19 age range, you can do it formaly at a sixth form but that mean you will have to do three A-levels and it would take two years. It will be free if you're British and you'll have teachers and tutors to help you.
Mash'Allah two A-levels in one years is very brave and ambitious. I wish you all the best. If you need any more information or help with how to do them privately, syllabus, structure, exam boards, difficulty etc then just ask me. I know everything.