High Caroline. Thanks for your suggestion. Golden Acre Park got back to me and it turns out to be a salvia - Salvia involucrata ‘Bethellii’. Who would have expected to see that plant in not-too-sunny Leeds! The Estate Manager told me that this plant needs very good drainage in the wet north to survive but it obviously can with the right care.
I grow Justicia carnea here and it gets through winters with a little die back. I take a few cuttings which I put in my little plastic greenhouse just in case we ever have a hard winter. However, it even survived "The Beast from the East" a couple of winters back which took us down to -7°C for 3 or 4 nights running and frozen snow. Perhaps it is tougher than we think.
