Leveller, the Tradition isn't a movement, its a process. It's an umbrella term which encompasses all the local traditions you describe.

The East Anglian tradition and that of the North East are quite different in style, and often in repertoire. However they share the same characteristics of a body of music passed around, shared and changed within their communities and it seems perfectly reasonable to me to describe that as "the tradition" when one is talking in broad general terms.

Although these traditions may have been very local, in the sense of each community having its own repertoire and possibly style, they were also open to outside influences and were always keen to absorb new material from wherever they could find it. This is why we get versions of the same songs and tunes turning up all over the place.