CGB the MSD you refer to alows for PEC aircraft position error, equipment tolerance and the GA manoeuvre.
John Eacott are you seriously suggesting that flying the GS at the very few international airports that have ILS in Oz you will be less than 200 feet MSD during the approach! I know its hard and trendy to accept greater risks down under but really!
You guys can hypothesise all you like. For me I will execute an immediate GA if my RADALT tells my I am at 170 feet MSD during an ILS where the state minima is 200 feet.
For all the usual heros out there that want to be as low as you can and think you can stay safe...good luck.
DB