Stop talking out of your ass.

I can't find an example in the twenty seconds I went looking, but there are any number of cases in the US where people have been sent to jail for killing people who illegally entered their homes. The one I specifically remember is the guy who heard someone outside his house, got his gun and waited for the guy to come in and then shot him. He got convicted of first degree murder, IIRC.

And having someone come into my house and commit further crimes is not the same as hearing someone leaving and then shooting them in the back. One of the guys was obviously already out of the house.

This does not excuse the burglary at all, and the guy does have the right to protect his stuff (if not with a gun in the UK), but he already did that, and then killed the guy anyway.