Self defence in the UK is currently a bit of a grey area. The law states that resonable force can only be used if there is an imediate or unavoidable threat of bodily harm to you and your life. Defending ones home is also a grey area.
The current law states
"The Criminal Law Act 1967 provides that a person may use such force as is reasonable in the circumstances in the prevention of crime, or in effecting or assisting in the lawful arrest of offenders or suspected offenders or of persons unlawfully at large. It is up to the courts to decide what may be considered reasonable force."
In recent months the Justice Secretary and the government have tried to put some clarification to the matter and have advised they will clarify the law on self defence in forthcoming legislation. The key is all firearms and shotgun permits in the UK are issued for sporting use only.
This is the current Justice Secretary Ken Clarke stance on it. As he states if someone broke in and attacked you with a weapon you can defend yourself.
BBC News - Justice Secretary Ken Clarke to clarify self defence law
There have been many docummented cases of burglars being killed or injured and no charges raised against the home owner. The issue arriese in cases like the Farmer Tony Martin who in 1999 shot and killed a burglar and injured another. At the time this occured the burglar was fleeing and the firearm used was unliscenced. This resulted in him being convicted of murder and issued a life prison sentance. However after 3 years he was released
Tony Martin (farmer) - Wikipedia, the free encyclopedia
However the flip side is Kenneth Faulkner 2004. He was a 77 year old home owner and victim of multiple burglaries. he lived in an isolated farmhouse with no close police presence and became under attack so shot and injuerd a burglar with a legaly held shotgun. No charges were raised agains him and the judge who sentenced the injured burglar said he could not critizise in any way the actions of Kenneth Faulkner the home owner.
BBC NEWS | UK | England | Derbyshire | Shot burglar case sparks debate
Same with Gary Holmes who shot an burglar who had an Iorn bar. This case was intresting as it was an airgun that does not require a permit unlike a liscenced firearm or shotgun. The burglar when shot dialled 999. however after a brief spell in hospital was charged for the buglary and the home owner was commended for his actions in protecting his home and his wife and baby
Burglar dialled 999 when shot with air rifle after breaking into family home | Mail Online
My guess is that there will be further clarification when the Riots have finished as it has been on the news today that 3 shop owners have been killed attempting to defend there properties last night