Thanks for that Roboraver. Sorry for being ignorant but what is MCOL?

I let my property to a letting agent for a fixed period of 12 months. The letting agent even issued a written Rent Guarantee for the 12 months whether they were able to rent the property or not. There is no break clause in the 12 months agreement. Now in the fourth month of the agreement I have received a letter from them giving me one months notice that they will be returning the property back to me. Can they do that and what are my options. Thanks in advance