Umbellifer Belles

We had an excuse to visit Badby and walked up to the scramble course atop Arbury Hill (the highest point in Northamptonshire, apparently). The path took us through a gorgeous hay meadow which abounded with all sorts of long grasses and meadow flowers - most unusual to see these days. I couldn't get close enough to this little coterie which gathered there to get a better shot but they still look nice. Can anyone tell me what sort of butterfly they are?