Hey MissImp0ssible, welcome to the forum.
It's a funny question, because the band has toured in many many countries already. But you're right, they haven't been to UK yet. Anyway, to answer your question:
They do try to take the local audiences of each country into consideration the best they can. Sometimes it's by saying "hello" or "thank you" in the native language, but they don't speak all of those languages fluently. At gigs outside Finland they mostly speak English, so have no fear, I'm sure you'll understand most of what they say in between songs during a concert.
The list of where they've toured is following: Finland, Sweden, Norway, Denmark, Germany, United States, Estonia, Russia, Ukraine, Lithuania, India and Romania.
(From the 'About Poets' page.)