So... I thought some of you might be interested in seeing the kind of airgap you need to prevent sound transmission (even where you have 8" concrete walls).
In essence the airgap is a minimum of 200mm at its narrowest point.Here's the view down the airgap when you walk into the main room from the kitchen and look right:
Here's one from the aircon chimney:
And here's one from where the storeroom off the control room:
