In response to Dave's sighting below, I attach two pics of a helice female that I found at West Williamston in August - perched, and just taking flight, the latter a bit blurry as the blighters always perch with their wings closed.... I've also clocked 5 male Clouded Yellows in all this year, three different individuals at West Will, one in Milton and one flying across the road near Gumfreston!
...and for comparison, the Milton male, on purple loosestrife