You could sit exams as a home educated child would, as a 'private candidate'.
You study however you can, self study from books, online courses, or a tutor etc. Then just pay a School or exam centre to sit the exam.
You cannot (easily) do anything with course work. Many private candidates take International GCSEs (IGCSE) for this reason. Sciences and English language for instance, will probably have to be IGCSE. So you will have to change syllabus.
Art PE Music will be impossible at this point.
Your parents will need to find somewhere that will accept you as a private candidate. You could try "tutors and exams" or local private schools. It is getting very late to register now, you will have to be on it straightaway.
Exams will cost about £150 to £250. More for subjects like foreign languages that have speaking and listening tests.
Remember, you only need 5/6 GCSEs for college and university.
Also, all is not lost. You can take things more slowly and get qualifications at a college next year instead.