I've used Radio Garden for years to help with language learning. In English language communication I can't stand the ads one bit. But in another language even those are an opportunity for practice.
Of course the news on any station is going to use more formal language, and the entertainment programming even on the flagship is going to use less formal. Just, the talk station from a flagship broadcaster - like BBC Radio 4 - is going to have the most bang for your buck in language instruction.
Seems obvious, but bears mention. Enjoy!