Not sure about the ID for this bug. The closest match I've seen is the European Hawthorn shield bug! It overnighted on the wheelie bin lid. Images 1-3 were taken on 29 May, under different lighting conditions than for image 4 taken on 28 May.
Thanks very much Aussiegall. That's a species I hadn't come across and, yes, I think you're right. I will suggest that as the ID. I have found some examples on Atlas of Living Australia. One is similar in colors to this one. Apparently, the name has been changed to Sastragala versicolor and only one confirmed sighting on NM (South Coast).