Why not try propagating it from cuttings? You might also try Jinny at Seedhunt to see if she has seed for this.

Thanks for the suggestions...
Seedhunt is not offering it this year, and as far as cuttings go, my plants get a bit worked over by the frost and at the ideal propagation time I don't really have any shoots to spare... Even Silverhill isn't offering it this year. Hmm. What to do?
Dan