I asked Rickie Lee’s backup singer Amy Barlow in '79, and I don’t think she know what “P.L.P.” meant either.
Brit here - I grew up in the 70s knowing PLP was a “public leaning post”. Dad would claim he wasn’t one - but I can’t say if it was a British thing or something my folks picked up when they spent a year or so in LA in the late sixties.
I had always assumed that Chuck E. was none other than Chuck E Weis.