But of course there is no way of complaining when the PEL (or whatever we call it) is not applied for.

My point there was that, if the proprietor of some premises, such as a pub or a cafe, would be quite happy to have a session or a singaround, but is unwilling to jump through the hoops involved in getting a licence that would make this legal, that is not going to show up in the planning process at all - and accordingly it won't be likely show up in any feedback to a review of how the Act is working.
And yet that is the kind of thing that is really likely to get in the way of people who would like to start up informal music in their locality. So it is important that people make strenuous efforts to record this kind of thing and make sure that it is brought to the attention of any review, and the local press.

The other important thing, of course, is that "the local nay sayers" are drowned out by the local yes sayers! Musical delegations to planning committees when this kind of thing is coming up would be one way.