Does anyone know if there's anyway of knowing what stock AUS Ralph Lauren shops recieve, so I don't have to drive to 4 different locations that are over an hours distance apart and not finding anything.
It's pretty inconvenient!
Yes. A phone.
Look on the US/UK site, find styles you like, then call your stores to see if they have it. If they don't, they might be able to order it for you. The RL store closest to me seems to be similar to those near to you (basic items, no Purple Label/Black Label/RRL), but people there can help get stuff not in store. They do work on commission, after all, so it's in their best interest to do so.
If you actually buy something from your store through an SA, they'll most likely add you to their client list, where they'll send you pictures/updates on new stuff via email when it comes in.
If you're that desperate for RL, you might consider asking someone on here in the US to proxy an item for you. With fee/shipping, it would probably be around AUS retail anyway.