Butterfly nooky?

Although not remotely adept at butterfly identification, from what I can find out this could be a pair of Black Veined White butterflies mating. But disturbingly, I’ve also found a report that the Black Veined White is currently extinct in the UK! So I’m very confused indeed. At one point I thought these looked like Green Veined Whites, but the patterning seemed different from the identification chart. I do hope some butterfly loving blipper can help.

PS. Have checked http://butterfly-conservation.org/ and it looks as though this lovely pair are Green Veined Whites. Thanks to lynnfot for the info. about the website. Thanks.