Nice to hear from a fellow Canberran.
Although we must live in different parts -- I don't think I've seen another diesel yet. Your 7.5 is pretty much my around-town average too. Although I'm still getting some 'real world disconnect', as I call it -- 7.5 is usually more like 8.0 when calculated manually at the pump.
Let us know how you go if you do get the tune. Even without towing a caravan, I think the diesel is a touch under-powered. I reckon the 2.2L diesel they sell in Europe sounds like it would be just about right.