I don't remember ever seeing "Brighton Fuck" as a working/alternative title for BR.
Anyway, over to our favourite archivist for your answer Martin:
Greg Brooks (2002): "Happy Little Fuck was the working title of this song. It was further referred to as Happy Little Day, Blackpool Rock, Bognor Ballad, Southend Sea Scout, Skiffle Rock and Herne Bay. Session engineer Mike Stone is the likely culprit of some of the titles, though like most other bands, Queen frequently employed working titles during the song development process."
Gullibility and credulity are considered undesirable qualities in every department of human life -- except religion.