That is a rough one. There are so many ways to cook it. I know of one where you get the oven nice and hot and then shut it off. It relies on the slow cooling rate of ovens to cook the meat. I never tried that myself.
My best prime rib that I ever cooked was using the sous vide method. Pick your level of doneness. Cook for about 6 hours,, there is a minimum time, but if you go over that nothing really bad happens unless you go hours over it. Then for the last 15 minutes sear it in a hot oven at 45 to 250 C. I did a perfect medium rate that way. Extremely juicy. Nice crust. It was better than any that I have had at a restaurant.
I don't have a sous vide so unless you can get yours to Aus in 8 hours that's not much help.