I got this plant from--where else--Heronswood, many years ago. They had them listed as plants that you had to specially ask for because they weren't growing in pots, but instead were kept as roots in the refrigerator. So when I purchased 3 of them I got 3 thread like roots kept moist in a paper towel. I dutifully planted them in 3 separate places in my garden and waited. It didn't take long for the wispy, delicate looking vines to come up, but it took them a couple of years to really get established and take off. But take off they have and now in certain parts of my garden they are everywhere. I don't really mind this because they are easily removed from places I don't want them. They scramble up any vertical plant they encounter, but the vine is not so dense as to smother any of these hosts. They look particularly good on conifers, providing a dash of scarlet color to an otherwise dull and boring plant. They are just coming into bloom in my garden right now and they will bloom pretty much into the fall.
I have read that they thrive in climates with cool, moist summers, which is apparently why they do so well in Scotland and probably why they do so well in my garden. I wouldn't say we have moist summers, but they are certainly cool.
These vines probably do not do so well in pots, which is why they are hard to find in nurseries. That is just a guess because I have never tried to grow them in a pot, and I could well be wrong. However, it is true that they are hard to find. Seed is available from a number of sources including Chileflora and Plant World Seeds.