which education board and a level should I pick for an extra subject?

am doing ICT level 3 BTEC extended degree right now and I'm feel like I can do another a level subject along side my course. I would like to do maths as that subject. But all the education systems got me confused, I don't know which one to pick and there is A level maths, AS maths and further maths. So if you guys have any experience please let me know, which one is most universities looking for ?

Nobody can tell you which one universities are potentially looking for unless you can tell us what degree course you'd likely be applying for.

You've referred to "A level maths, AS maths and further maths". The term "A level" refers to a type of qualification, as does the term "AS level". An AS level is worth half an A level and is unlikely to be of much interest to universities. Further Maths is a subject, and can be taken as an AS level or an A level qualification. It would be very unusual to take Father Maths without also taking Maths.

So, based upon what you've said, A level Maths would seem to be the most appropriate qualification for you to take alongside your BTEC.

Your BTEC (which is an Extended Diploma, by the way) is designed to be the equivalent of three A levels. So by taking A level Maths too, you'd be going from three to four, in terms of A level equivalence.

Thank you for your reply, i would like to do computer science in university. What exam board would you recommend ?