Isn't it odd that in all three places you mentioned (Australia, Canada, London) you don't have the right to defend yourself with firearms?
Interesting point. Some years ago a young delinquent (he was 16) broke into a house at night armed with a tree branch to bash someone. However, he broke into the wrong house and the owner of the house, who was alone, happened to have a loaded .243. In the darkness he took aim and shot the intruder dead. He was never charged but the mother of the dead youth was adamant that he should have been. The law is that you can use no more force than is necessary to protect yourself.