Sorry to get picky here McGrath - but that ain't so . . There are many documented instances of landlords having been told that they need a Public Performance Licence to continue having Music in their pubs. In some cases the Licencing Authority has acknowledged that they were acting without any complaint being received. A number of folk clubs have closed as a result.As for lock-ins - clearly there are few "good" landlords, then (but round here the music and the lock-ins may coincide but only alegedly, of course).
Your "take it outside" suggestion is true only if the musicians go far enough outside to be off the pub's property . . as evidenced in the recent "Council bans morris dancing" thread. And in any case that's then different laws that would be likely to be applied . .
G.