Don't nettles encourage some kind of butterfly. They lay their eggs on them or something?
Also - didn't I read that some butterflies (red admirals?) come here from Spain each spring?
Red Admirals are now reckoned to be able to overwinter here, but a lot more do fly in. The main immigrants though are their Vanessid cousins "Painted Ladies" (there was an invasionof them about 5 years ago, I remember seeing dozens around Newhaven. Also Clouded Yellows fly in at some time most years.
Having said that I understand there are rumours that the "Monarch" butterfly might try to establish itself here, this is a true worldwide species based mainly in America but has spread to Australia and I believe the Azores. It can fly for hundreds if not thousands of miles.
https://en.wikipedia.org/wiki/Monarch_butterfly