LEASEBACK COMPANY IN TROUBLE

I HAVE A LEASEBACK 50 / 50 WITH A COLLEAGUE. THE COMPANY THAT PAYS US HAS NOT DONE SO FOR APRIL AND WE HAVE RECEIVED EMAILS SAYING THEY HAVE FINANCIAL PROBLEMS. DOES ANYONE KNOW WHO WE CAN CONTACT TO SEE WHERE WE STAND LEGALLY ON THIS ? THE PROPERTY IS UP FOR SALE BUT POTENTIAL BUYERS ARE PUT OFF BY THE LEASEBACK. COULD WE SELL THE PROPERTY AS 'VACANT POSSESSION' IF THE COMPANY HAVE DEFAULTED ON THEIR PAYMENTS TO US ?