How about 'Baggeridge Country Park Folk Festival' held on 2nd,3rd & 4th of September. Its a free festival but you might have to pay for parking & camping. There are a variety of performers including those of the traditional kind. Very friendly with chances of getting involved in music / singing session. I go every year and I and performing this year.

Baggeridge by the way is in the Black Country. There is a festival web site, whose address escapes me for the moment but a search on the web will get you there.

Go if you can and enjoy.