If you have any countervailing evidence, you are welcome to present it. As it is, the best evidence is that Brett Osborn is doing prison time because he killed a man in defense of himself, his friends and loved ones--in his home--when he was confronted with a deranged intruder. There could scarcely be a more clear case of self defense, why did this this get so far as him doing any time?
Osborn is doing time, not because of his actions in the house, but because of his actions in the court. And if there is blame for his poor judgement that lies with anyone other than Osborn himself, it lies with (according to his own statements in the press at the time) Tony Martin. Martin's statements regarding his case were widely reported and caused much confusion, which was not a victimless crime, as Osborn shows. Fact is, had Osborn gone to trial, he had a better than good chance of being acquitted according to what little evidence we do know of (of course, as pointed out, we don't know the full, verified story and so there's an element of doubt, but there's a lot of leeway in the law for cases such as his). But because of Martin's reported story (which differed substantially from the story the physical evidence told), Osborn chose to plead guilty to a lesser charge.
Because as a pratical matter, the English do not have right do defend themselves. They are expected by their government do to nothing to hinder criminals outside of calling the police and with stiff upper lips laying down for the miscreant do as they wish.
Codswallop.
The right to self-defence in the UK is not, has not been, and probably never will be under attack. There is no requirement to lie down and be beaten. There is, however, an apparent difference between UK and US definitions of "reasonable force". However, according to a recent Crown Prosecution Service statement (the approximate UK version of the DA's office), in the past 15 years, only 11 people were tried for murder in "self-defence" cases, and those were well outside the boundaries of reasonable action. For example, knocking out a burgler, tying him up and then setting fire to him.
There is also the difference that if you shoot someone in the UK in self-defence, that's perfectly legal - but if you shoot someone in the back as they run away from the house with your TV, that's not. And rightly so - despite their immoral act, burglers do still have a right to due process, and to deprive them of that when it's not necessary to do so is frankly, unethical. And yes, at 3am in the dark when you're scared, that's an academic distinction, but the law is constructed in such a way that if you act honestly and without malice, your actions will be legal. And it's hard to fire on a fleeing man without malice...