Complicated Possession and Arrears Case

Rent Arrears

I have a 6 month AST with a Limited Company called Cuckoo Homestay, signed by the sole Director. They are an agency who place immigrant workers in local houses in various locations around the country. The AST is with this company but after 2 months they have stopped paying becasue they said they had not received enough rental from the workers agency. They are now 2 months in arrears with 2 months to go on the remainder of the AST agreement. I think the workers they had in there have moved out and the workers agency has stopped paying the Limited Company completely. As my AST is with this company I have told them that it is their problem and they are still contracted to pay the rent for the full 6 months. What is the best way to tackle this situation. If the property is now vacant I could change the locks and start marketing it again. If I can fill the property within a couple of weeks that will mean the company only owes me 3 months rent arrears. I cannot predict when the property will be filled again so how can I make a claim for a particular amount of rent arrears now when I cannot say exactly how much in arrears they are. At this very moment they are two and a half months in arears but it could be 3 months arrears or 4 months arrears depending on when it is re-let.