Sorry I've not repied before.
Hi Stoorty
At the end of the season I simply took cuttings of shoots with no flowers / buds. Deleafed and shortened. Stuck them round the edge of a pot and popped them in my utility room. Last year i managed to take two into the summer, this year 4 have survived over winter. The ones I lost were either because they just didn't root or got some mildew. They were actually in the same pots as my geranium and lobelia cuttings. I try all sorts (I have about 30 ox eye daisies that I didnt thing would take, but they have), some work some don't but you never know til you give it a go.
Sorry my reply wasn't cleverer!