In the UK, a 6 Cell Maglite is the answer. Since you're liable to prosecution for using disproportionate force, regardless of the situation (i.e. you're protecting your family & property during a break-in), a big Maglite at least can be considered a secondary, not primary weapon. They're well manufactured, heavy duty, and make a decent block/strike weapon, if you're willing to practise swinging it a few times.
I also have a set of side-handled night sticks, should I decide that ensuring the wellbeing of some c*nt that's broken into my house isn't of primary importance. Again, a great block/parry weapon, with the option to strike.
If you went at someone with a knife there's a good chance you'd end up in prison, even in self-defence. The law is deliberately ill-defined in the UK, so lawyers can make lots of money defending people. IMO, the rule should state that if you enter someone's property uninvited, you give up all protection from the state.