Yes thanks for the response. I still have only five seedlings sitting under a cloche on the bathroom window sill and they are about 6" long - that's about all I can say. The hot weather does not seem to suit them despite keeping them moist and there has been some die-back which I trim off and live in hope.
I first saw these in Carol Klein's page in the Garden News when she said she had ordered some of these in February this year, presumably as established plants. I tried to find out in e-mails to GN what the outcome was but never got a reply. I believe that they are pretty robust once established and they originate from South Africa, where presumably they will have to be fairly tough to survive. Give it another year and mine should be quite well established although when there will be any flowers is an open question. The plants Carol Klein showed on her page were not from her garden but an image of what she planned to order this year and the flowers in the picture were orange.
Thanks again for replying.