"A spokesman for the society said that royalties were crucial to songwriters and musicians and music shops received a 30 per cent discount."

Yes, we agree royalties are crucial - but wait a minute. Isn't a "royalty" an agreed percentage of money paid for the performance? It certainly was when I worked in the accounts dept for Decca in the 70s. Lets say that the publisher has agree a royalty to the composer of a piece of music of, let's say 10% of sales. Then in the case of somebody trying out an instrument playing notes from the piece 10% of money paid to the musician for playing (£0) = £0.00.

The other scenario would be - what if I go into a shop pick up a banjo and play something that I have just made up - will I then receive a payment from PRS?

Somebody needs to kick these bureaucratic assholes into check. Sue the bastards for harassment or trying to obtain payment using menace.