I am currently studying The Access to HE Diploma and one of my modules is Biology. I bought this book a short while ago, and I can not put into words how helpful it has been with my studies. It follows a wide variety of topics that is so well written, I haven't once gotten a headache from reading about the information inside. It's complete with images, revision questions and even things that can set your mind away wondering why certain things occur within the human body. It also has exclusive web downloads.
This site was also the least expensive for this book, as other places are charging a lot more for it.