I have not yet heard German folk music on the radio in Germany in my twenty-six years of full residence here. There is a programme on German TV called "The Folk Music Hit Parade" (I kid you not!) However, this is actually a form of pop music for people who keep their teeth in glasses at night and have not yet heard of The Beatles. There have been one or two threads here, on which unsurprisingly, the most interesting posts have been from Susanne and Wolfgang. As Ralphie pointed out above, real German folk music (no easier to define than British or US folk music) has had a bit of an image problem since the national socialist era. There was a very fine tradition of narrative and subversive songs. In particular, "Die Gedanken Sind Frei" was not a favourite of the Nazis. I have occasionally heard a few fine musicians playing traditional tunes and dances. We have at home a wonderful collection of Jewish songs recorded by Zupfgeigenhansel. However, this is very much a minority interest even in Germany. Although there are pockets of interest here, I know of no folk clubs or sessions dedicated to German folk music. The nearest thing to a folk tradition which I can think of, which is common currency throughout Germany, is the tradition of passing on childrens' songs in the kindergartens. Every German will recognise the tune of "Alle Meiner Enten."
From personal experience I will also mention that the British have little patience with other languages. An attempt to sing the lovely Yiddish ballad "Oj Dort'n Dort'n" provoked outright annoyance on one occasion. It may be a shame that some of this lovely music has gone unheard in Britain, but it does not surprise me.