It's a service that's available only for members of the RHS. Every year you get to choose up to 25 packets from the seed they collect from RHS gardens (mainly Wisley and Rosemoor, I think) for a fee of £6 to cover administration and postage. The list is usually published around October and the offer closes at the end of January. They have seed of annuals/biennials, perennials, trees, shrubs, grasses, and also some interesting greenhouse plants, including climbers. Take a look at the seed list on the RHS website.(http://www.rhs.org.uk/seedlist/seedl...5_seedlist.pdf)