Grey area. There was some toff bird interviewed on the radio saying that the amount of householders who use what force they see nessecary to protect their property, sometimes a little excessive, who DONT get prosecuted is massive. Her opinion was that the laws didnt need to be relaxed due to this statistic.
Its the media that blows everything out of proportion and puts it in the public spotlight, "they love a good shooting"!
In our current anti gun state (which is only getting worse) the use of a firearm would still be deemed as excessive, BUT it would all come down to circumstance.