Girona, Catalunya, Northen Spain
I doubt they would be interested in propagation, they just buy in potted plants and have very little knowledge of those they do.
It is pretty vigorous (needs a good chop back again), does take my frosty winters ok, to -8 and shrugs off snow, so I think it would be fine in milder parts of the UK.
I’m not really a fan of variegated foliage but this one is quite subtle, lights up the semi-shady end of the border and sets off Salvia Amistad beautifully.
I would say the flowers on mine are creamy white, lemon would be a stretching it, but they are tiny and disappear in the foliage. I will take some close-up pics next year.