The right to kill burglars

I'm a bit confused by this. While I can get gleefully behind the populist feel-good idea that some scumbag who burgles your home is fair game, I have a niggling feeling. Or rather several.

1. Isn't reasonable self defence already protected in law?
2. Define burglar. Would there have to be signs of forced entry? Is an unlocked door OK or does there have to be broken glass or something? Does the person have to be holding an item of your property at the time of the baseball bat hitting their head? Is there any threshold in value of said item?
   
3. What happens when someone gets killed by mistake?
4. How does this sit with the 80 or so reasons an empowered person can use to force entry against a homeowner's will? What reasonable measures must a homeowner take to check a 'burglar' isn't a perfectly legal gas engineer who has smelt gas at the property?
5. While I think that a bona fide burglar deserves everything that comes their way, let's just indulge the bleeding heart liberal bit first. They might have turned to crime to fund a drugs habit. These people need help before it gets to that point.
6. Once you've got druggies out of the equation, that probably does leave your despicable career criminal. But then, they probably shouldn't be able to commit the offence in the first place because they should still be in prison for their previous crime.
7. Then there's the timing. At the same time Ken Clarke wants to reduce the size of the prison population and the Tories are going on about Big Society.