Housing Benenft

Other

My tenant has been in receipt of Housing Benefit for years now and rental payments have been sent directly to me at his request because of personal issues he has he could not be trusted with the rent.
10 wks ago H. Ben suspended his claim because his claim was under question, I have kept H. Ben informed every 2 weeks that we had not received the rent and kept them informed of a runing total of the amount of the arrears and the duration of the arrears.
On week 8 I advised them that we were now serving Notice of Possesion however during this entire period they have continued to pay the tenant directly.
The Notice of Possession expire yesterday and at which point we applied to the court for possession, however this morning I have received a letter from H. Ben to advise the tenant moved out on the 1st Nov, I know for a fact he has not because he has been seen in the flat together with his now claiming H. Ben elsewhere and has pocketed the rent owed to us.
H. Benefit have advised tough nothing they can do to help and cannot give me his new address either (data protection)
Can anyone give me advise on how I find this tenant to try and attempt to claim the unpaid rent and get a CCJ put on him and attachement of earnings too.
Thank you