I eventually came to the conclusion that PE passengers can use the UC toilets, because I've never been told otherwise, on any annoucement...

Makes the 2 toilets in UC very busy at points though, but came in handy when flying PE once. Most of the time it's me as UC passenger waiting for another PE passenger coming out of there...

I've felt it should be UC exclusive though. Especially in the LGW flights, where its your only loos.