In central Northants, the bigger towns were Soul havens, Wellingborough, Kettering, Rushden/Higham, and the smaller nearby places, Irthlingborough, Raunds etc were grebo places. Irthlingborough and Higham Ferrers are but a mile apart and of a similar size (5,000 pop in the 70's) Higham is full of "soulies" while Irthlingborough has few.
The Newton Aycliffe example is really interesting and I often wonder why a large town like say Peterborough has a long history of Northern Soul while Coventry, twice the size of Peterborough and smack in the middle of the London to Lancashire soul belt has, apparently, very little soul activity. :search: