Most of the varietal names for C. flexuosa are taken from the shade of the flowers, Jon, so you will have to go back next month to check this ;-). There is one called 'Purple Leaf'; the leaves tend to be a bit darker than the ones on your plant - maybe they darken with time or your could be a hybrid between Purple Leaf and one with green leaves. You would have done better to have asked whilst you were at the halls.

This I know! I was too busy snapping everything! Thanks for your help though.....