I went to the bio headstart lectures last year, they were good for exposing you to the unit 3 course for the first time, but you'll unlikely remember everything they said, that you won't hear in class for a while. Their notes are comprehensive (3 booklets like nerdmmb said) with an answer booklet as well. They cover the entire unit 3 course, but are not very succinct and contain some unnecessary information that you don't need to know. Still are valuable though. Also don't make the mistake that I did, by going to the unit 3 revision and headstart lectures (around May) - their the same notes. For unit 4 notes - winter school. They're not essential though, especially for the price.
If you haven't already, I'd listen to Douchy's biology podcasts (just google it), I found them more useful, even more than my teacher. For methods and spesh I don't know - going to methods this year.