As a musician and singer of some years, I am quite taken aback by the awesome standard of some of the new performers now coming onto the scene - a lot of them but not all, coming from the Newcastle Uni folk degree course. for musicianship look at 422 band, they are excellent.
As far as I understand, many of Bellowhead particularly the brass come from a professional background and play in many other genres when not in folk music. I fully appreciate that some will and some will not like the Bellowhead approach to folk music, but surely what the "scene" needs is some who will preserve the traditional sound and others that will make experiments with it and create new approaches to traditional material.

That said, I do agree that if performing for a fee, singers and players should be presenting polished material. Folk clubs do however have to provide a facility for new singers to practice their trade and if this was not available, any performer would never know whether they are likely to make the grade or not. I suppose the position we have have is that whereas, in the olden days, folks would stand up in their local pub and sing "their"song for the benefit of the crowd, we now have a situation where people have paid to go into a folk club and are perhaps quite right to expect a minimum standard of performance. I too do cringe also when singers do not at least try to present a polished performance.