I have found a website that has all of the AS and A2 OCR biology papers that have been available since 2001. While these papers are not the current OCR syllabus, they are still a very valuable resource. The other A level syllabuses are similar enough in content to make it worthwhile downloading these papers and attempting the majority of the questions. I estimate that 75% of the three main exam boards overlap in identical content, but be aware that you would not be expected to do 100% of the content from a syllabus not your own. If you find a question that you really don't understand or recognise the content - it may be that you are not required to know it!

Try www.pastpapers.org for papers and mark schemes.

If anyone knows of similar websites for other exam boards, please tell me as I've not yet found them.