There is a large patch of these plants fairly local to me. I think they are helleborine but can't find any exact matches in books or on line. They stand about 2 foot high and there are both pink and white ones. They are growing on a sunny hillside and are about half a mile away from beech woods. Some are growing up through bracken and others standing proud above the brambles! They are covering an area equivalent to a small field and are the most glorious sight!
They are not helleborines, they are Himalayan Balsam (sometimes called Indian Balsam or Policeman's helmet) - Impatiens glandulifera. They are an extremely invasive species, and are very difficult to control. There are river banks near me which have been almost completely taken over by them, to the exclusion of many local native plants.