I used to fly in to the PFA at Cranfield back in the late 70's and early 80's. It was licensed ATC but the r/t phraseology drifted away from CAP413 simply because it had to. Quite often you would get " if the aircraft ahead of you lands on the right side of the runway then you land on the left, and vice versa". It worked but was way outside the book!
Never been to Popham but it sounds like a fun event. Unfortunately in this modern day and age you will find a line of 'regulators' just waiting to screw the 'safety' lid down on this just as soon as something nasty happens.
Imposing full licensed ATC on an event like this will only serve to slow things down whilst the controllers labour under modern day regulation.
Things aren't what they used to be.