I think most of these dances are easier in the more confined controlled space of the studio. The bigger scale of Blackpool usually means extra dancers and enormous props, which my impression is that most of the audience don't like. They will all have to up the theatricality of it all, and while having a charleston is much better than having a rumba or a foxtrot, it might not suit Blackpool as much as a VW or something hyper-intense like a paso or an AT, because with the charleston it's often about smaller details. Georgia's charleston would still have been great if she'd had a week later but I doubt it would have worked quite as well as it did in the studio.
Having said that I think the charleston will really suit Helen and it should be a good dance for her.