It depends what you want to study. But generally, to study science at university, you need to have passed all your science and maths GCSE’s with a C or above. You will also have to take at least 3 A levels and 1 AS level in a relevant subject. Typically you will want to study maths and at least one other science at A level, but this is not always the case. The grades you need in your A levels to study science at university depends on what university you have applied to, but you will be able to check these out on line and by ringing admissions departments nearer the time. Like chris said too, go and have a chat with your career adviser, or visit your local connexions centre http://www.connexions-direct.com/index.cfm
I think Natalie is wrong about the need for 3 A levels in a relevant subject. This depends on what degree you are planning to do. So for some like medicine or vet school the choices are really prescriptive. But for others you can be a bit more creative. So for our sports science degree (one of the top rated in the country) we require 2 science A levels but prefer 3.5. The last A and AS level could be anything as long as you could say why you chose it at interview (and got a good enough mark to get in). But GCSE Maths and Science (Double Science minimum) are pretty much an absolute requirement. I also think whilst Natalie is right that we scientists like students to do Maths this is a very rare REQUIREMENT for science jobs. If we made it required we would have to close down over 70% of science degrees. But the key is to look at what you want to do specifically and plan in advance. Take advice and look at UCAS pages. There are lots of jobs in science that don’t require top grades. We send a lot of students with solid, but unspectacular, grades to rewarding, secure and very useful jobs as NHS laboratory biomedical scientists for example.
I didn’t say maths was a requirement, but it’s top of the list of advisables. It’s pretty hard to do any science without a decent foundation of maths. This is why a lot of degrees have to offer calculus and statistics catch up classes. If you do A level you don’t need the catch up classes so you can study more interesting aspects of your science subject in the place of these during your first year. It depends on what you want though. I studied science with only one full Science A level and an AS science and the other two subjects were not related. If I went back I would have taken Maths, however. Some universitys are quite strict with their entrance requirements so its always best to do your research before you pick.
It wasn’t the maths bit that concerned me, but the requirement for three “relevant” A levels. A lot of science degrees don’t require this as you yourself found out. For example the psychology question we had earlier. Psychology degrees hardly ever require three science A levels.
Of course there is a difference between what is needed and what is optimal. I am struck by the number of people, like yourself, who later in life wished they had done a more ‘core’ subject like maths or chemistry. I, myself, dropped physics, but now have a PhD in Biophysics. In my school the curriculum and the teachers were boring in physics. No relativity or quantum ideas, just trolleys on slopes with ticker tape. I am still suffering from this loss.