Tom, I don't doubt what you are saying is correct. However, PRS does not charge by the song, neither is the charge made direct to the performer. It is the venue which must obtain the PRS licence. The PRS argues that it is impossible to guarantee that a copyright piece or arrangement will never be performed, and a single performance is sufficient to trigger the need for a licence. This assumption is probably realistic, especially for folk clubs where there isn't a fixed set-list and anyone can stand up and sing, often without knowing the copyright status of the song.

I'm not sure its good news that the tariffs are set by an independent body, as that appears to remove any possibility of negotiating in individual cases.

The PRS's tactics have not only been discussed many times on here and other music-related forums, but stories appear from time to time in the national press. They seem to be oblivious.