Anyone remember Tony Martin?
Yes. He obtained a gun illegally and shot people in the back, having planned to do so beforehand. That is a long way from self defence.
It's illegal to do anything more than ask them to put it back and please go away is the result of that from what i've heard.
And I've heard that aircraft contrails are the secret world government dispersing mind control chemicals.
Everyone hears a lot of twaddle, especially nowadays when it can be spread so easily.
Just go to the Home Office website and you can find the real position. Or, if you care to spend rather more time getting a more detailed picture, you can look at records of court cases. Try to find one of someone being convicted on any charge from any form of defence. The handful of convictions involve things such as prolonged beating before throwing the intruder in a pit and setting fire to them (and yes, that's a real case of "self defence").
There's now a legal precedent partially sanctioning attempted murder in revenge. The attacker in that case got a suspended sentence and even that was portrayed as being pandering to the rights of criminals, denying people the right to defend themselves, blah blah blah.