Was a piece on telly (Trevor McDonald) the other night about just such a thing. Yes there has to be a plate within so many metres outlining the restrictions ie the hours that you can't park. If there isn't then the lines are not legal and the ticket can be contested. Apparently the local councils throughout the country are ignoring the legal requirements in many places and are relying on the ignorance of motorists just to pay the fine.
Good advice re:the camera get it photographed if there aren't any signs, best of luck