Under UK law you *do* have a right to defend yourself. You can even kill someone if you have a reasonable suspicion that your, or another's life is in danger (this is despite what the tabloids would have you believe). If someone came at me with a knife and I was unable to run away, I could kill them and the police wouldn't charge you. Similarly you may use 'reasonable' force at any time - stabbing granny might not be reasonable in this case, but punching her might be. You just have to get over the natural revulsion of using violence against someone in your care. As I have always believed, "Better to be judged by 12 than carried by 6".