The RHS process a diverse range of seeds from plants cultivated in their gardens. The list is extensive, i.e pages and pages and pages long and has all manner of things from simple Bidens to magnificent Betula (yes of the tree variety!)
A couple of years ago I bought about 20 packets completely forgot about them, on the whole and on finding them this spring grew the host that had not dried up beyond recognition. Forgetting what you have ordered is part of the fun so there were some rewarding surprises, Coreopsis grandiflora being one of the and Water iris another, the peony has yet to produce anything but I am patient. The Rosa chinesis went in and out of the airing cupboard and fridge so many times I lost count and it probably forgot how to germinate, I have abandoned that one.
The 2012 list was published on 1st November and of course you have to be a member to be able to benefit from the stash of fabulous seed matter.