MCPS-PRS are bottom-feeders
PRS have been chasing small businesses in my local area lately and can be nastily persistent in demanding you pay up, threatening legal action if you refuse. In my view their tactics are a form of intimidation and similar to MPAA/RIAA in nature.
The implication from the outset when dealing with them is that you are breaking the law, that they have full government backing to pursue you, and the more hassle you give them in getting money out of you the more it will cost as they may need to send an inspector round, they may need to investigate previous years infringement, etc, right up to a potential court prosecution.
I saw the Out-Law coverage on the Kwik Fit case from last year, and the charity forced to pay up so kids could sing carols for charity, and knew they were bad news then. Having had them on the phone a few times at work I expect even more aggro in future, they just don't want to give up, even told me our hold music on the phone was a breach, except it's copyright of the phone manufacturer.
I could understand shops playing music for customers having to pay, although I thought that was already covered by PPL, but they want to be paid for any form of music played outside the home; from radio in your lunch break including internet radio, news or talk radio, car radio in a work vehicle which seats more than 1, all the way to hold music on a fricking phone! whether it's the public or employees hearing it.
As others said, the radio stations pay an amount based upon potential listeners in their coverage area to broadcast it, but they want a 2nd/3rd/4th bite at the pie...scum.