A lease/Tenancy is a legal interest in a property. If the ownership of the property changes, that interest is not destroyed. This means your tenancy will persist through and after the property sale. Tenants still benefit from all their tenancy rights as described by the law. None of them are limited, altered or restricted by the change of ownership.
Section 21 eviction ( no fault eviction) can be served on the tenant by the Landlord to get back the possession of the property.
Tenancy does not terminate with the expiry of the fixed term, if the tenant stays on , the tenancy rolls into a periodic monthly tenancy.
Tenancy does not terminate by the eviction notice as well. If the tenant stays in the rented accommodation, after the expiry of the fixed term and expiry of the eviction notice, the tenancy rolls into periodic monthly tenancy , and Landlord would have to get possession orders from the court to get the possession back of his property.
And tenants have to leave by 14 days of the court orders , and If the tenants remain in the property after the possession orders by the court, then Landlord can get the possession orders enforced by the court bailiffs , who can evict all the occupants from the property and handover the vacant possession of the property to the Landlord.