In the case of an Assured Shorthold Tenancy, the tenant has the right to remain in the property for six months, unless they break any major terms of the agreement. The tenancy can be terminated by either party after this time without providing a reason for termination if the tenancy agreement allows for this.
If the tenant is in breach of the tenancy agreement, then the landlord may be within their right to apply to the courts by a serving the tenant with a section 8 notice of seeking possession. This is a formal procedure and landlords must outline the specific terms the tenant has breached.
Landlords are entitled to dispose of any belongings left in the property two weeks after the tenancy has terminated, but endeavors should be made to have the tenants retrieve their left property.