Here in south-east England it's not a rare bug but quite local in large woodlands. When I was a kid just collecting locally I dreamed about finding them but never had, when I was old enough to drive I was happy to drive an hour to big colonies to find them. During the heatwave we've had for the last week I've been out walking locally, not far from where I grew up and I've seen them in six separate places within 5 miles of my home. Whether they were always around but I never found them 50-60 years ago, or whether they're expanding their range I don't know, but they certainly seem to be a lot more common than they used to be.
Is it a Martin White reintroduction site, do you think?
No I phoned Martin the week after my discovery to clarify, he said he hadn't been within 30 miles and wasn't interested in introducing paphia. It is a natural spread north as it is with the white admiral L camilla which is only about 40 miles south of me now, I reasonably expect camilla to be resident in 10 years.