Let your hedges overgrow without trimming, is not just an aesthetic issue affecting the presentation of your house. In Australia (at least in NSW), the overgrown hedges could attract a lawsuit if they are severely blocking neighbours’ views or sunlight. Check this news in NSW.
You may want to go to http://www.lawlink.nsw.gov.au/lec and see Tree Disputes.
To see the content of the Trees Amendment click here.
In Victoria, Whittlesea, Knox and Maroondah city councils enforce a rule of clearance of overhanging tree branches from the ground level to 2.5 or 3.0 metres when over a footpath.