Steve - "no worries" is an Ozzie-ism that has been around for many years. Back in the day when I was a Sweet Young Thing people - always blokes, women weren't supposed to know such things - would sometimes say "no wucking forries".

Another dating back a very long time, and still in use today, is "she'll be right". It can also be combined with "no worries" to make the compound phrase "no worries, mate, she'll be right".

Once again, a bloke thing. Women have their own Womenspeak. There is also Familyspeak.