As you say memories of the same era obviously differ. If you PM me I can send you Derek's contact number and you can sort it out with him.
I don't suppose he would thank me for speaking out on his behalf, and for that matter I am not qualified to.

The MCPS, PRS and Publishers generally do indeed work in a mysterious ways, and indeed over 30 years of full membership of all the collection agecies have left me with no clear view of their operation - only a fleeting impression of rather turgid, expensively produced publications that they send through the post. The state of one's confusion about their various functions has (I have found)no real bearing on whether the money arrives.

Down at the working men's clubs during the 1980's most of the cabaret artists were knocking out cassettes for a couple of quid. Most were professionally produced. they helped keep music live, by makinga bit of petrol money for the artists, but I don't suppose the publishers saw a deal of licence money from them. Still as we said, our memories of the era differ.

As for your last point. Well sometimes people who can't afford it, if the rules are strictly applied, want to use your music. perhaps they won't bother if they know they are going to be named and shamed. A common sense point, I should have thought.

anyway, best of luck with your song writing career.