After coming back to WAB after 3+ years away I find your message. It would be rude not to respond (however belatedly). I seem to recall that I never saw many as a kid growing up around Bath, but since moving further East they seem common as muck during their flight period (early spring). It's best to look out for them on the sunny side of wooded areas - or even individual trees. In flight they don't look much like moths - more akin to a swarm of midges from a distance & they are surprisingly hard to pick out once they land.