Oh man. I just remembered the name of the book that I suspect of playing a large part in traumatising me into my bathroom/plumbing phobia. It's this one:
http://www.amazon.co.uk/Magic-Lavatory-Red-picture-books/dp/0099974401 It probably says something that my initial Google searches were for things like "evil lavatory" and "demon lavatory" and "lavatory of death". Man, a psychologist would have a field day with me. 1p for a used copy. I think I will buy it and see whether I can lay some ghosts. Bet I can't. :D