There's Chris Roche's/Dave Pleasants' shanty crew (the Shanty Crew) too. And keep an eye out for where Knights and Mageean are booked. They do a lot of shanties so places that book them may have other shanty stuff too.

Oh, and the Shipwright Shanty Crew if still going.

Hard Pressed are probably too far west for you.

And Swinging the Lead although I think their base is Dartford.