Update - both these species came through last winter completely unscathed on our chalk bed. Multiflora came up quite early, behaving like a normal herbaceous perennial and put up with some harsh weather. The longiflora are just emerging as I write, in May, but look strong.
A glorious night-scented species - the fragrance redolent of tropical evenings. (The very long-tubed white flowers are typical of plants pollinated by moths.) A low spreading bushy perennial with rather sticky green foliage. Very vigorous and easy on the dry chalky raised bed at the nursery, and could well be hardy enough to survive the winter outside (USDA zone 7) in a sheltered spot with rain protection. If not would also be fabulous in a big terracotta pot on the patio, brought in for the winter.
Update - ours are re-emerging in our dry raised bed, along with several seedlings! Definitely worth trying outside then, at least in dry sunny sites.
1L pots ~ £6