In the UK you will likely face prosecution for standing up to an intruder in any way, shape or form. Yes legally you're allowed to use reasonable force but the legal establishment cannot make a judgement on what reasonable force is, so they drag 12 random people off the street to make that judgement for them. Don't worry though, being prosecuted is really in your best interests because it gives you free access to a lawyer.
Likely, my arse.
The CPS are well aware that a person claiming defence will probably only be convicted if they used deranged levels of force, so far beyond reasonable that a bona fide sociopath would be able to see the distinction.
As a result, it's very far from likely that you will face prosecution for standing up to an intruder unless you torture or kill them after they're no longer a threat, i.e. torture or kill them for your own enjoyment.
Arrest is quite likely if there's any doubt, but not prosecution.
An example from someone I know. They were directly involved in this incident:
The police are called to a disturbance in a house by someone nearby.
When the police turn up, they find a wounded man lying on the floor bleeding and an uninjured man, apparently under the influence of drugs of some kind, holding a machete in a threatening manner.
The police order him to drop the weapon. He says he won't drop it, talking somewhat incoherently about needing to keep it. The police make him drop it and arrest him.
When questioned at the police station, the machete-wielding man claims he used reasonable force in defence.
The police investigate and determine that the evidence indicates that his claim is true - he was defending himself from someone who attacked him with a machete and managed to take the machete of the guy who attacked him with it (who was injured in the process). He was still in fight mode (flight was impossible - one door, guy with machete between him and it), jazzed up on adrenaline and not thinking at all clearly and still fixated on "I must have control of that machete so it can't be used on me", when the police rushed in just after that happened.
He was released without charge, i.e. not prosecuted.
Next time you read some of the usual ranting about how criminals have all the rights and victims will be jailed forever if they even look threateningly at the criminal stealing from them and threatening to kill them, blah, blah, blah, bear in mind that it's cases like the above. Man arrested for defending himself when attacked by machete-wielding madman! Then even that gets exaggerated ridiculously until some people really believe that UK law only allows a victim to say "Please desist from stabbing me, that's a good chap", and then only if the victim also offers to help the burglar carry the stuff they've stolen.