Well Swallowtails have now been reported from Strumpshaw, Upton Fen and Cockshoot Broad. No news on Norfolk hawkers yet though.
I've just noticed the caravan link: I used to live nearby to that site. Can't comment on the site, but it's perfect for accessing Strumpshaw, and you are ten minutes from Cooper's Wood local nature reserve, and just opposite the site of a prehistoric henge. It's halfway between cooper's and the damselfly walk shown here:
Dragonflies of Norfolk - Sites - Norwich - Damselfly Walk