Leave in your room. If the furniture allows, wrap a strap around something and padlock it to itself. To be honest though, if someone is very determined to take your stuff, they'll find a way. However, I've never had a problem at all. If you're checking out of your accommodation and have a day left to explore, check it into to one of the public lockers at a train station or similar - most of them have some.
Think about it though - would YOU really want to steal a pack of someone else's stinky clothes? didn't think so
The trick is to never take anything travelling that you can't stand to break/loose/get stolen and not to worry about your belongings too much because it'll take the edge off the adventure.
What the hell are you lot on about? Money belts are awesome! I travelled half way around the world with one by land and wouldn't have felt safe without it. Painting a target.....WHAT! No one would have got that belt from me without sticking there hands in my boxers and pulling it out from beneath my bull bags!
In Austarlia / Nz it is very safe, safer than the Uk I reckon. so just carry a wallet like everyone else for your money.
As a uk citizen just take your own visa card anywhere in the world and it will work fine (Nationwide is best) No need to get a ozzy card unless you're gonna work in oz.
Try and leave any valuables with the hostel staff, they should have a safe. Just make sure that they sign something to say they've received it.