I would look to see if Sony sells the VAIO SVS15123CXB or similar laptop in Australia. Pricing would be different since I believe things cost more in your country even though the difference in currency value is relatively small.
It has a Core i5, HD 4000, 15.5" 1920x1080 resolution screen and it is 4.42 pounds which is pretty light given it's size. If I were in the market for a laptop, that would be the one I would most likely buy even though I have a strong preference for Lenovo ThinkPads.
Check with budget PC first since they claim 2 year warranty on this laptop (make sure it is). If it is not (they make a mistake and there is really only 1 year warranty), then go to the store that is closest to you.