I generally think of it first as East Anglian, but have seen variants from several parts of the British Isles.
Whist at a Folk dance festival in Germany this summer, I also saw a Danish side doing a slow broom dance, with several elements in common with 'standard' British broom jigs.

Broom dancing is old, so it's very hard to tell if someone knows about it as they saw it a few years ago, and thought 'we can do that', their ancestors saw someone doing it hundreds of years ago and though the same, or if it was drempt up locally, or indeed any combination of these...