mmm...could be that one or both have lost their jobs in this current climate or they just don't want to pay. some tennants do just this - pay for a while and then stop, forcing the landlord to be patient. you now have to make a decision. they are clearly in breach of their tenancy and you have every right to give them notic and then go down the court route to evict them if necessay. this can be a long, expensive process and you could still end up with no rent. only you can decide how patient you are going to be. good luck x