I don't have much experience with quilts, but I sleep in the 4 and on my side also, and every other which-way, and have found two bags that work great: one Montbell and one Western Mountaineering. I used the Montbell as a quilt once, and that worked fine. I'm a cold sleeper and only 5'6", so you'll have to look among the related options in the links below to decide which one would best suit you. I got one of them on ebay and one on the gear swap here, and those may be good options for you, for shipping to Australia.
Western Mountaineering Sycamore, or try another of their semi-rectangular bags. Here's a comparison chart:
Montbell UL Super Spiral Down Hugger (800)
It looks like sometime this year Montbell has re-assessed the bags' temperature ratings and made them more conservative. So if you're not getting a brand-spanking new one, google the specs from some pre-2012 write-up, and compare them to current ones to get a more realistic picture. (For example, I have the #3; it has 10 oz of fill, weighs 21 oz, and had a temp rating of 30 degrees F. The new 2012 #3 has 11oz fill, weighs 22oz, has a lower-limit rating of 30 and a comfort rating of 40 F.)