In the past, I've emailed a couple of you my old notes from when I did the RHS General certificate. I've updated these a bit to match the 2009 syllabus and tidied them up a lot and put them up on a website, as part of a school project on building web pages.
http://www.learnbotany.co.uk/index.htmlIt's by no means complete - don't have anything on the garden design part of the website and some of the pesticide references are out of date and the website needs some better layout. The science-y parts on plant biology & soil science are pretty thorough though.
Hope someone finds it useful.