Some of these Polish folk singers as you put it Tunesmith are probably descendants of Polish war veterans who fought alongside us Brits in the second world war and were based in our country. Quite a number of these war veterans remained in this country and have brought up families here. They are as entitled as much as you or me to be classed as folk singers if that's what they do.
A couple of friends of mine wrote a song about Polish war veterans who were based at Faldingworth RAF and I had the great honour of going to see one of the polish veterans to get his approval of the song. Him and his wife still live near Lincoln and are such lovely people.