I don't know about song, story-telling, or other forms of dancing (e.g.display or celidh). I do know that even up here in the NW the Social dance community think a lot of it. Clubs organise holidays there.

As far as Centre of Excellence I can see that while in the normal pub / club scene you have what you get, the people who go to Halsway are probably more committed to improving, and because you are mixing with experts you learn a lot.
A little oasis away from 'real life', which you go back to inspired.

I've never been to Halsway (or to Burton Manor which also used to run weeks). But for me Whitby festival does the same thing.