Your landlord must follow strict procedures if they want you to leave their property, depending on the type of tenancy agreement you have and the terms of it. More information can be found on the GOV.UK web pages.
If you wish to vacate your rented accommodation there are processes to follow depending on what type of tenancy you have. It is important to follow the correct procedure otherwise you may still be charged rent even though you are no longer living at the property. Take a look at the information on Shelter's (England) web site about renewing or ending a tenancy.