Messing up completely, best option?

Hi I've tried searching the forum but nothing really answers my question :|
Yesterday I sat my Geography A-Level paper and was estimated A/B. I completely messed up the paper, figures were incorrect, wrong case studies etc. I know I will have failed the paper, and geography is the only subject that was carrying me into university as English and Biology are not my strong points. All I needed was 200 points but because of this, I'm sure I haven't got nowhere near. I'd like to start finding out options before the results come so then I'm prepared. I would really like to continue Geography at Uni, is there anyway I can resit the geography paper say at like Christmas? It would be just that I'd need to resit. Or is there any other options that would help me into getting into uni the following year? I'm just confused! Any help would be appreciated