Omg - I emailed a e group I belong to on Monday and asked the same question Roy, I know the best place to see them is Norfolk (where I am going for the weekend)
I got a reply from the Norfolk butterfly recorder:
Quote:
You're a bit early I'm afraid - flight season is usually from mid-May to end
of June with a smaller second brood in July - early August.
Best places are How Hill, Strumpshaw Fen, Wheatfen, Catfield Fen and
Hickling Broad. (In that order I'd say).
If you're around the broads next weekend your best wildlife spots would be
Winterton Dunes to Horsey (Seals, Cranes, Adders and migrating birds plus
possibly first brood Wall Brown and Grayling butterflies). If you're near
the North coast then Titchwell RSPB and Holme Dunes is a must for migrating
birds, while if you're near the South then Lakenheath RSPB might have the
first Golden Orioles by then while Weeting Heath has Stone Curlews. Also
Foulden Common for Dingy and Grizzled skippers.
