its very harsh with speeding over there compared to here. There is just so little leway anymore, barely the width of your speedo needle. We have 10% + 3 although not advised to quote it if pulled over doing that! Its fine on the motorways when all the traffic is moving along at 120kph ish, they will leave you alone. If you are the only one doing that and everyone is going slower, they will get you then.
I do agree with having it stricter like you guys do in built up areas as there are so many kids who just run out without looking but in the middle of no where like the Hume!?