Welcome, George!
It is usually easier to propagate them from seed, though the colors won't come true. It can also be dug up and divided, but the roots are brittle and easily detached from the crown, so there is a fairly high mortality rate that way. When starting from seed, it is usually 2 years to flowering.

Thanks for your thoughts. I think I will try both methods. We have one plant that is about five years old and it needs thinning out anyway. Do you have any experience of the dwarf variety. I am told they are not hardy

If you are thinking of the "evergreen" kinds sold as living bouquets at the florist, my experience might not count. They grow in the winter here, but we rarely get hard frost. Since they don't really go dormant, I would expect them to need more shelter.