Rob,
I would agree with a lot of what you said. The atmosphere at the Ditchling session is great (though I hated the acoustics of the room at The Bull) and open mics and singarounds play an important part.
What they don't have and what a folk club does and should have is the ability to bring a variety of the very best performers of varied ages and styles to an area. The ability to see top singers and musicians in an intimate atmosphere should be inspiring to non-musician enthusiasts and to the area's aspiring musicians. The folk club is in a unique position to do this and will only succeed if it takes on this role. If it descends into being a gathering of regular old cronies that does not seek to achieve the presention of excellence then inevitably it will fail.