Eviction query.

Rent Arrears

Hi,
I recently let a property using a local letting agent. They provided the tenant, vetted and referenced him etc. The tenant paid the first months rent and an equal amount as a deposit. He failed to pay the second months rent and used many stalling excuses. The 3rd months rent was due last week and despite many promises made to the agent, he has failed to pay. He is a working man and his income is more than enough to pay the agreed rent. The agent informed me that we cannot have him removed until 6 months has passed.
Is it true that legally, a person can pay 2 months rent and occupy the property for 6 months?
Your advice would be much appreciated.
Thanks, Tony.