We saw these fat boys on our walk the other day. Good news is that Toby decided the second one was 'scary' and ran away. An excellent tactic we wish to see from our dog towards reptiles. (The first one he missed entirely.) The other good news is that where they have decided to live is the most likely place snakes would choose as well (note the pipes behind them) - therefore we hope that's decreased our chances of Toby (or us!) coming across any of their venomous cousins.
These are, it appears, the common Eastern Blue-tongue Lizard - Tiliqua scincoides. We're not entirely sure about the blue tongue. I mean would you go "Say aahhhh!" to check?
More details here.