I have to reply to this after a long long time - 6 months after I posted this item I was involved in a serious road accident that put me out of action for 20 weeks and now I have come back here with very different circumstances - anyhow I have found out the mystery of Plotopahlea. The author of the book about the history of London area of Kilburn has discovered that my guess was right and the word was a misprint when someone made an error in the typeset for printing copies of the flyer for the Fete in 1884. He and his co author found a second copy of the same poster publushed in a magazine of the same period and in place of Plotopahlea was the correct word Photographer. Obviously the side-show listed with Punch and Judy was a new novelty having one's photograph or portrait taken and presumably the print developed while you wait. So there is no such thing as Plotopahlea and the mystery is now laid to rest.