First point, he must give you 24 hours notice to enter the property. Landlord and Tenants Act 1985 section 8.
Was the house tidy? In most tenancy agreements there will be a clause pertaining to keeping the property in a good state. If any clause in the agreement is broken the landlord may serve an eviction notice at his own discretion.
If you believe that your landlord is breaking the law you can speak to the council who should have a Tenancy Relations Officer who has the ability to press charges if it is necessary.