I picked up a leaflet about the above in Ilam today. It’s another invasive non-native species which the government are asking us to control. A local project is currently underway with the aim of tackling it in this area.
The plants have purplish-pink slipper-shaped flowers just now, and when the seed pods mature they explode when touched, scattering the seed up to 7m away. We think we found some in a corner of our garden and have dug it up.
If you think you might have some you could check the picture at http://www.invasiveweedsagency.co.uk/himalayan-balsam/