Evicting A Lodger
If you are living in the same property as, and share facilities with your occupant, then they are a lodger or excluded occupier - not a tenant. Lodgers are protected by the 'Protection from Eviction Act 1977'. The notice that has to be given is 'reasonable notice'. This is usually taken to be the same as the rental period, although it can be less in cases of severe breach.
If you have a contract/agreement with your lodger then it may give them more security that the Protection from Eviction Act. If this is the case, they your breach of the contract could result in a civil claim from the lodger.
It is best to serve notice in writing, and to have some kind of proof of service. It is impractical to use the postal service to your own address so personal service with a witness is preferable. Having a guest or friend present at the time of service will also reduce the possiblity of friction or adverse behaviour from the lodger.
If your lodger refuses to leave then you can not physically eject them, but you can refuse them entry back into the property. This may involve changing the locks. Once the notice expires, the lodger is trespassing in your home, you may be able to get help from the Police. If you think there may be a threat of violence then it would be wise to involve the police - they will usually try to attend if there is the potential for a breach of the peace.
If you do this, although the lodger has no right to re-enter the property, he does have a right to his possessions. It would be best to arrange an agreed time/date for these items to be collected and to have them available for hand-over at the front door, or alternatively for the items to be collected from a secure storeage place. If it is more convenient for you to allow the lodger access to your property to collect his goods then you would be advised to only do this with a police presence.