Yarrow (Achillea millefolium) is a widespread and tough as old boots grassland perennial (lawns too). It has a long flowering season over summer and into autumn; I saw plenty of it when I was in Dorset several weeks ago.
 Generally the flat flower-heads are a pure or creamy white but in the middle of a field near Cattistock I saw a swathe of Yarrow in shimmering shades of pink.