Fool, how many guys can hear the radio at your work? and does the place run shifts?
Have a look at:
http://www.prsformusic.com/SiteColle...riff%20AWE.pdf
You might be able to whip up enough to get a licence. They won't back date you, they will have no evidence that you were playing music beforehand. They may try to make you pay a higher rate for the 1st year tho.
The other way to do it is to get you're fellow workers to reduce their workrate, and get the supervisor to point out to the bosses how much the lack of music has changed productivity.
Or just buy a MP3 player.
The reason that this payment exists is that, legally, a playing of a peice of music, in a public place is considered, legally, the same as a live perormance, and the artist is able to ask to money for a performance. PRS just collects the cash.
It's morphed over the years, but that is what the PRS' business is built on.
As I said, a lot of artists need this money to eat. Most factories get a PRS licence as a matter of course these days, I'm surprised your hasn't tbh.