Looks like ASOS have extended their 30% off everything by adding a new promo code.
Tip to decrease prices even further - use a different country’s store (and still getting delivered in Australia). I’ve found the Turkish store using Russian Rubles being the cheapest option! You can get a chrome plug-in that checks this for you on every item, or there is an asos price checker website.
Cash back won’t be eligible, but the discount compared to AUD is around 10-20% so more than the current cash back amounts!