Can I do only 2 a-levels?

Hi, for my 6th Form subjects I chose Core Maths, Computer Science and BTEC Science but I ended up having to drop Core Maths to resit because I got a D in GCSE despite the fact I was told the minimum grade to do Core Maths was a D. 😕😠 Anyway, so now I am doing Computer Science which is a 1 year course I think, correct me if im wrong) and BTEC science which I believe is a 2 year course. I was offered to do Product Design but I don't think I want to do that after the teacher expects me to do summer work on a subject I barely know and I was also offered to do Media which doesn't really interest me. Is it possible that I just do BTEC science and Computer Science this year and just BTEC next year because surely after all this is my education therefore my choice. :/ I don't think the school would agree though. Something else I was thinking of doing was if I pass my resit of Maths this november maybe I can rejoin the Core Maths course and do that. I am really confused atm so I dont know what to do. Any comment is appreciated.