The first swallowtail was seen today, 19th May, at Horning. As was Brown Argus at Wereham.
We now have 21 species flying in Norfolk: Dingy Skipper, Grizzled Skipper, Swallowtail, Brimstone, Large White, Small White, Green-veined White, Orangetip, Green Hairstreak, Small Copper, Common Blue, Holly Blue, Brown Argus, Red Admiral, Painted Lady, Small Tortoiseshell, Peacock, Comma, Speckled Wood, Wall and Small Heath.
large skipper should be the next seen.
Paul, from your description I saw the same green hairstreaks on Sunday (or at least three in the same location with one perched and two chasing each other).
I've has a description of two painted ladies seen flying purposefully yesterday near Norwich. The observer reported them as flying "like they did last year". We might be in for a small influx in the next few days - though it's unlikely to be on the same scale as last year.