There has not been any change in the law. It's the same as it's been for years.There is a legal right to act using self defence but theres a thin line between self defence and GBH/ABH. I've been there before - had a knife pulled on me but managed to sort the situation but I was taken to court over ABH but charges dropped as luckily there was a CCTV camera watching!
The law was changed that should someone break into your home and also should your life feel threatened... so if they hold a knife/gun or whatever to you... You can defend yourself and if that means you killing them (remember if your life if threatened) then its within the law!
We had a huge debate about this at karate and I was right! Someone dragged in an off the street coppa!
If the deceased was killed in self defence the householder has no case to answer.