AQA AS Biology

I'm thinking about taking AS Biology next year along with my A2s as I think it will be more interesting, and useful than doing an EPQ, it has been a year since I have done any Biology and got and overall C in Additional Science GCSE...

Any recommendations about what I should do over the summer (things that I need to learn etc) so that I can be in a similar position to most people also taking the course? Thanks

They're letting you do Biology AS with just a C in additional science...? Gee low standards or what? XD
You could buy CGP'S AQA AS revision book and try and learn some of the lower end AS level stuff: https://www.cgpbooks.co.uk/Student/books_as_science_biology_aqa.book_BAR52
You could look through the exam board's specification: http://filestore.aqa.org.uk/subjects/specifications/alevel/AQA-2410-W-SP-14.PDF

You absolutely MUST ensure you know the GCSE knowledge in the following areas so you can learn the much harder AS stuff, if not, you're going to have an extremely hard time:
Cause of disease
Lifestyle factors of CHD and Cancer
Interpreting graphs
The immune system
Vaccines and Antibodies
The Digestive System
Proteins (amino acids) (how to test for them).
How enzymes work/what affects their rate of reaction. "Lock and Key model" AND "Induced Fit" model to get a headstart.
Animal Cell Structure. You could learn the extra ones if you wanted an advantage. (Plasma Membrane, Nucleus, Lysome, Ribosome, Endoplasmic Reticulm (ER), Golgi Apparatus, Microvilli and Mitochondrion is as far as you go at AS level).
How cells are adapted to their function. (You could learn epithelial cells in the small intestine to be at an advantage).
Diffusion
Osmosis
Active Transport
Lung Function
The Heart (how it works).
Cardiovascular disease (the factors which increase risk).
Genes/Meiosis
Parts of a plant cell.
The Cell Cycle+DNA Replication
Mitosis
Cell differentiation
The Circulatory System+different blood vessels+tissue fluid.
Water transport in plants.
Antibotics becoming resistant.
Biodiversity.