Silverhill Seeds does not have an internet address, but they do
have fax/phone. I have found that their selection is somewhat limited,
so it is worth your while to get an updated list from them directly.
As for viability: this year, I ordered a selection of about 10 different
CP seed types, and only one has not germinated in 5 months. (an
unknown drossera - "from the Chiminimane Mountains in Zimbabwe").
If you need further/expanded details, contact me.
Regards,
John Kneen
jkneen@aerotek.csir.co.za