Is it true that East Europeans are more interested in dancing than we Brits, and are more successful at it.
If you put a query such as 'paso doble final 2013' into YouTube there seem to be thousands of clips, and the majority seem to feature East Europeans.
Even competitions held in Blackpool and Bournemouth seem to be dominated by people with names such as Malitowski, Zagorouitchenko, Torokgyorgy, Chesnokova, etc, etc.
The OP mentions Prague. Prague seems to have been the location for a World Dance Sport Open Event, in September (and you can find dozens of videos showing that).
It might help to explain why so many of the Strictly pros are not native Brits. IMO, the influx of talent into Strictly has improved the show.