Dolichos lablab (or Lablab purpureus), the Hyacinth Bean.

http://www.growsonyou.com/photo/slideshow/164531-hyacinth-bean/member/fractal

I thought this was so pretty I looked it up - The hyacinth bean grows as a vine, producing purple flowers and striking electric-purple coloured seed pods. Lablab bean is a good choice for a quick screen on a trellis or fence. It grows fast, has beautiful, fragrant flowers that attract butterflies and hummingbirds, and it even produces edible leaves, flowers, pods, seeds and roots. Dry seeds are poisonous due to high concentrations of cyanogenic glucosides, and can only be eaten after prolonged boiling
Do you think it would do well in the UK Fractal or would it be too invasive?

Certainly not invasive as it is just grown as a summer annual (perennial in warmer climes). The picture link in my last post is one I grew at work this year. It is fast once it gets going.

Did not grow for us here, our season is just too short for things like this.

thanks all for help. those seeds we planted this year (took the pods last year from arestaurant garden!) have each now spread to about 3 metres wide and 1metre high, and still creeping. have had many requests for seeds when ready.