Posted: 29/10/2013 at 17:47
Thanks everyone. My original plants did survive through the last winter, without any help from me, so I'm hopeful they will survive again. (Thanks for the advice about putting a little fleece round them punkdoc.) I was eager to have some healthy cuttings so that I can have some more plants in the garden next year. I've never seen this variety of Diascia in garden centres before or since.
I'm going to try putting the cuttings in my porch. It is double-glazed and fairly bright. It has no direct heat but is obviously warmer than outside.