They get arrested, of course! Unlike in the US, this is actually considered a crime to shoot someone robbing you.
Their MP,Alan Duncan, said: "If this is a straightforward case of someone using a shotgun to defend themselves against burglars in the dead of night, then I would hope that the police will prosecute the burglars and not my constituents...The householder is the victim here and justice should support them and prosecute the burglars."
Anyway, the robbers and the homeowners are all in police custody.
Now, where exactly does this concept of gun rights come from anyway?