Its not like you have to have prior knowledge when moving onto A-level history. As i'm doing history at GCSE, we do a lot about Germany and Britain. However the A-level course that i'm moving on to, is about the super power relations (mid 20th centuary) and the British Raj in India.
So i would advise you to look at the course, see what it is about. Perhaps even look at an exam paper and see if the questions are manageable towards your skill sets. And if you do decide to do history, you'll definitely be taught all the required skills as well as the content.