Pieris brassicae Large White
Wild plants aren't necessarily on this butterfly's diet as it just loves any member of the Brassica family. Cabbages are obvious targets and other crucifers such as oil seed rape can attract Large Whites in numbers. I managed and unusual (poor) photograph of it in flight going from Spear thistle Cirsium vulgare to Spear thistle and in October (well outside it's supposed flying time) too.