Left 4 Dead 2 - Game Instructor is now appearing and I cannot disable it?

[NeilF]

So I regularly play L4D2 and suddenly yesterday the game switched to seemingly wanting to give me the Game Instructor before spawning an infected and I cannot turn it off. I've tried turning off the Game Inustructor in the Multiplay options, and even adding lines to config.cfg:-
gameinstructor_enable 0
cl_autohelp 0
cl_showhelp 0



Any clues how I disable it?