Hi robzy, You could try to get in touch with the Mornington Peninsula Astronomical Society
http://www.mpas.asn.au/
Out the other side (way other side) of Melbourne is the Snake Valley Astronomical Association, just past Ballarat (
http://svaatest.site88.net/)
Also the Astronomical Society of Victoria (
http://www.asv.org.au/) has a dark sky site just north of Heathcote.
Of course you would be obliged to join up to these groups eventually to continually use their facilities.
Another wasy of finding a dark location out form Melbourne, is to meet/know someone who lives on the outskirts of the suburbs and ask them if you could impose on them.
Just some suggestions.