How do I prove rental liability for housing benefit.

altinkum1

I rented a property over 6 years ago for a 5 year period, at the time I was on housing benefit - filled out all the forms - gave in the rental agreement and all receipts to the council and was paid housing benefit. I have now moved out of that property, my personal circumstances have improved and am in the process of buying my own home.
Apparently the name on the agreement and on the rent book was false, I paid the rent regularly in cash to who I thought was the owner and now the council have told me that because i had have no proof that rent was paid (I have long since binned the rent book and even if i hadn't it still would have been no good as its in somebody else's name)have no rental liability as the name on the agreement was incorrect and the actual owner of the property has died with no body succeeding him!.
They have said that I have to pay all the rental payments back.
I have appealed against the decision and it is now going to a tribunal.
I can not prove "rental liability" as I was miss lead too and the money I received was paid out as rent - but surly I will not have to pay this money back. I believe in justice and I can not believe that I will have to pay it back but that is what the council are saying.
Does any body have any ideas?