Problem is that you are dealing with two types of law here. Criminal and civil. Criminal law is the law of the state and enforced by the authorities. Civil law is the law of precedent and what has gone before as being generally 'right'. When the two run together it can get very confused at times. If a person is bitten by a dog, in effect an assault, the fact that the person should not have been there isn't always taken into consideration. Did the dog bite the man? That is the question surrounding criminal law. Has a crime been committed? Righteousness has nothing to do with it. Now was it fair that the man was bitten by the dog? Hah, a very different question.
Thing is that in a case such as this, the Police can be very understanding, sympathetic and as they hate all scrotes might just say, nothing to see, move along. No crime committed. It's natural justice. In order to prosecute someone, the Police (via CPS) must be able to demonstrate that it is in the public interest. Ie that the tax payer would like to see justice served. In this case I think we have asked the people's jury and they have said, no. So the law isn't really a silly law here, it's a law that says people must control their dogs. Correct application of the law is what is questionable.
Now where that can go awry is if the Police have a particular beef or if the dog owner has overstepped the mark. Let's say there is a break in and the dog scares the scum bag off but then the owner send the dogs after them even though the threat has now gone. This is what really happened in the Tony Martin case. He was safe but still went after Fred Barras and killed him. Reasonable force is really about using just enough more force as needed to come out on top. Which in a life and death situation is why you can kill the other guy and it still be reasonable. Of course sometimes the cops HAVE to investigate because someone kicks up enough fuss to force their hand. Can't imagine this being the case here unless it's the council for some reason.
Anyhoo, that duty of care that we have had mentioned as being owed is a CIVIL duty. Not a Police matter. They don't enforce that. You cannot be charged and prosecuted for failure to provide that duty of care. Look at a car crash. The Police turn up and as long as they don't see that a crime has been committed - speed, maintenance, distraction, drugs etc = they drive away. They are only interested in an offence. Not blame. Injury is not a crime, it's a result of a crime. If they can't see a crime then they aren't interested in the injury. It's that simple.
So criminal law judged against a book of strict rules. You can appeal of course if you think that the rule has been misapplied or misunderstood etc.
Civil law judged against a history of what we decided the last time something like this happened. This can be changed though. Precedents are set but can be overturned and reversed which becomes the new precedent
Criminal cases usually take precedent over civil matters and historically if found guilty of a crime then being sued is easier as the duty of care bit is sort of proven by the criminal case. Not always though. If no criminal action is taken, this can strengthen the defendant's case against being sued, but again not always.
For there to be a civil case, it must be proven that there was a duty owed, that this duty was breached in a knowing, wilful, negligent manner and that any injury or loss was as a direct result of that breach. There is the impression that you can sue for just about anything and win, well you can't and lots of people fail but it doesn't hit the headlines. Sometimes the plaintiff wins the case (say a burglar) but the court indicates 100% contributory negligence. In other words it wouldn't have happened if they hadn't been there. But the facts of the case were that someone else who was not a thieving shit could have suffered the same fate. Let's say a child retrieving a football from a garden. So yes they can win but get nothing.
Anyway, all that aside, I truly hope this goes away mate. I have met your dog and he's soft as shite. Well he was with us that's for sure and frankly I'd like to see the law changed in favour of the home owner. There are too may softies out there who say oh but if you could batter theiving scrotes to death with bat with nails in it, you could entrap someone you don't like, invite them in then claim they were really scum and it was all a terrible misunderstanding. Right. So that's going to happen MORE than real break ins, is it? Bring back the death penealty - oh no what if you hang someone innocent? Sure, but what about the other genuinely guilty scutters that we execute and improve the world?