Don't forget that BSI ( or IMG) are paid for contracts with Poland and Sweden to also show all the GPs, in the same way that Sky does. Maybe Denmark shows them as well? So they are not totally dependent on the Sky money only.
However, the guys that are BSI are mostly British so naturally would opt for British riders.
The other point is, that Cardiff is not only attended by British supporters. Cardiff is full of Poles on the day, plus Swedes, Danes, etc.
I can see the day when they would not see Brits as a top priority. The Polish and Swedish Elite Leagues seem far and away superior to us now and Russia is maybe on the horizon. Add to that the number of good Aussies coming through over here as well.
Just my thoughts.