UK Copyright exists as soon as a work is created & PRS is an expedient way of royalty collection,alternatively authors can make a private arrangement or pass it up-ok,understood from the outset..

However,what rankles still is this:when a music venue opens up pretty shortly a letter turns up from PRS asking for their annual fee,to be distributed as they see fit, or face an injuction under the relevant Act.
It appears to be no defence to state that a) a high proportion of the music is live undocumented performance-a common situation for quite a few pubs I know.And/or b)they make direct arrangements with composers-admittedly unusual.
From Synbyn's note ( re.media plays apportioning)composers of pub rock probably loose out just the same as folk & jazzers.

Cheers F.(UK)
Cheers