Self Defence and The Law
Although it is our intention to get the best out of you as a self defence practitioner, we must also be mindful of the laws. The following statement has been taken from the home office website for your information on self defence. I highly recommend that any practitioner should be acquainted with the law; these laws can be read at libraries or over the internet.
The law relating to self defence:
You may only use “reasonable force” to defend yourself or other from an attack. What you see as reasonable force will depend entirely on the situation and its progress. For example, if you really believe you or someone is about to be murdered, then you can use any appropriate methods to stop the assault. However, this does not give you a free licence to murder the assailant. Likewise, if you have used a metal bar to beat the assailant, to the point where there is no further risk from him, you are breaking the law if you continue your attack. In essence, you must only use the minimum amount of force that is required to stop or avoid further injury to your self or those with you.
This is only a small quote from the home office website, even the home office acknowledge that every situation is unique to the individual and the attack.
Further details can be found here