Can you sit your computing gcse exam without enrolling onto a course?

No, you cannot sit a GCSE computing exam without enrolling on a course (or equivalent independent study that meets the exam board's requirements). Exam boards require evidence of structured learning and assessment to award a GCSE. Simply having self-taught knowledge isn't sufficient. You need to register with an exam centre, usually through a school, college, or other approved provider that offers the GCSE course and can oversee your examination.