Well, unfortunately many things that may be logical in US Law will come across as different to you, but you are wrong. For one, if anyone is shot in the UK then it is a big deal as people are not permitted to carry arms for self defense. So if anyone shoots another person, it is automatically, intent to endanger life, 'attempted murder' at least.
There are no homes in the UK that have a gun for protection.
It is illegal to own a firearm for the purposes of self defense, classed as 'possessing a firearm with intent to endanger life'. You shouldn't have one and the only way you could ever get off is if you were shot first, but you would still do time for 'intent to endanger life by the pure fact you had the gun.
So even if you have a license and a gun in the home, in the security holding that you must legally have, you are not allowed to use it to fire on anyone. Like I say the only giving chance is if you are shot first then they will show a little ease. It is a senseless law, but in UK, all guns are for sport purposes only, and shotguns are farmers tools for vermin control, kept under the same tight legislation.