Dropwort (Filipendula vulgaris)
As Dropwort and Meadowsweet look so alike this is a case of using other criteria to make an identification. Whereas Meadowsweet is a plant of wet (or at least damp) ground Dropwort thrives on dry chalk grassland. Similar plants, totally different requirements in terms of habitat.
Locally common but not widespread Dropwort is always a nice find in June through to August.
If you want to be totally sure which of the two species you have found then look at the leaves, they are very different. Meadowsweet has bold rose-like leaves whereas Dropwort are much more akin to ferns.