Shot one,
Most of the Aussies, Kiwis, Canadians working in the UK are in fact British citizens. If they are not, then they have the right of abode. Other wise, I would hate to think what the immigration is to enter the UK.
If a Brit had the same thing, then they can wander into Oz too.
Immigration isn't impossible into Australia. You would be surprised how quickly it can happen if you have the right skills.