If you can't get to a Myer store for their 30% off sale this weekend (July 9-10), or they don't have the items on their website that you want (which should get you free shipping over a $100 spend), then try ToysRUs for two weeks from July 13th, as they have "buy two, get the cheapest at 50% off" for selected Lego lines.

It may not be as good as the Myer offer, and not all Lego is included in this offer, but if you wanting several items and can pair up similarly priced items to buy them in pairs at the register (NOT all at once as the computer might pair up all the really cheap items with the expensive items), you can get up to 25% off your total Lego purchase.

The ToysRUs catalogue is here, noting that this offer is ONLY for - Technic, Marvel Super Heroes, DC Super Heroes, Classic, Friends, Nexo Knights, Duplo, Ninjago, Juniors, Minecraft... but I know a number of you here collect some of those lines.