Yes Sydney has also had some hot weather but I think you guys in Melbourne will have it worse. I hope your TFs and other action figures / toys will be okay. I do think the heat is not too good for the plastic.
The rubsign on my Classics Prime is also activated, despite the fact that I've placed it on a level of a bookshelf that's facing away from the sun, with the blinds regularly down! I think when living in units, the higher up you go the hotter it gets (at least that's been my experience).