In my opinion, I would say that savemyexams was pretty worth the money. I took Biology and Chemistry as well, and savemyexams was pretty much in my daily routine because I would use their topical questions everyday after I revised a topic.
Although some people argue that you can get complete full past papers online for free, it was just much more convenient for me for have them separated by topic. Their notes are pretty good as well, and very up to date with the specification points so you don't have to worry about any of the notes being irrelevant.