I could stand right next to you and you would not know whether I was armed or not. Not seeing a weapon does not equate to unarmed. Under the circumstances, one would about have to assume the intruders were armed.
The law does not allow you to kill some one based on an assumption.
Break into my house while I am home and I can promise you that you will never break into another. And I could give a shit if you are armed or not. I am not about to give you the opportunity to take the first shot.
Which is why you need a gun. Not criticizing, just explaining why there are so few guns used for personal protection this side of the pond.
And clearing up some of the misconceptioins regarding the law on the subject here.