If you understand basic wiring, how to insulate the circuit, and how to isolate the low-voltage circuit from the high-voltage (relay, transformer, or optoisolator,) I wouldn't worry too much.
I know what's safe and I've done a lot of electrical wiring (for myself and for friends), but I'm not licensed. (I have a brother-in-law who is an electrician, and once in a while I'll ask him about the codes.) I've also built lots of electronics projects, and most of those have included building a power supply, which of course plugs into the wall!
I live in the U.S. so I don't know about Australia, but it generally takes gross negligence or criminal negligence to get you into trouble. If you just make a "dumb mistake", your insurance should cover the damage. If someone gets hurt or their property gets damaged, you are liable for your mistake but your insurance should cover it.
Now, if you playing a game where you drive your car blindfolded, or if you are lighting fireworks inside your house, or if your illegal drug lab catches fire, you might get arrested, and your insurance might not cover it. 
I actually wouldn't worry too much about a fire. If you mis-wire something, or something shorts-out, the likely event is for the electronics to "fry" (maybe get hot and die without a fire) or a circuit-breaker in your house might blow. Everything would have to be "just right" for the device to heat-up, and continue to draw enough current to create a lot of heat and cause a fire, but not enough current to blow the breaker. (A fuse in your device is also a good idea.)
If you do something wrong, it's more likely that someone gets shocked or electrocuted, than to start a fire. So, make sure everyghiing is insulated and wired correctly. 