But it can be argued that Northumbria is only notionally English... The Romans drew the border in a more sensible place when they built the Wall.

Bring back the Heptarchy. I just don't believe that thinking about England as one single cultural entity makes any real sense. Though one of the oddest thing about the current folk-dance scene is the way you have groups performing styles of dancing from the other end of the country, which has nothing whatever to do with the folk tradition in their part of the country.

Border Morris in Kent and so forth. Nothing wrong with that, but it's not really that different from Samba Bands based in the Home Counties. (Which always end up looking more like Molly Dancers to my mind. Tradition will out in spite of everything.)