I wouldn't bother with a hydrostat, I'd just set them up so they'll always be moist. I use moist sphagnum moss as substrate.
Heat source depends of your circumstances and how you want to do it. Ideally I would just heat the room and not the enclosure. This is one of the few species I'm not actually fussed about giving a thermal gradient to. If the room never goes below 26 degrees and averages much higher I wouldn't heat them, but I doubt that's the case in south east QLD. But, if you do live in a well insulated house which does have that climate, I probably wouldn't heat them.
Assuming you will be heating them, it's a complicated story. A heat source which works in one enclosure might not work in another due to multiple variables. A few months ago I was talking to the guy who is arguably Melbourne's best known and respected Chondro keeper, and he said he was having a lot of problems keeping Chondros when he moved house, and he just couldn't get anything to work which kept them healthy, but the same heat sources and.enclosures in a different room of the same house fixed everything. These are fussy snakes.
I'd personally use heat cords, but exactly how I did it would depend on too many variables to describe here.
Maybe the biggest don't with Chondros is keeping them with less than about 100 snake years of experience, which takes most people 5-10 calendar years or more to accumulate.