I suspect this is benefit fraud and you should contact the benefit fraud helpline to report them.
I also think you should discuss getting payment made directly to you rather than the tenet while you are sorting out the eviction. The law around payment going to you rather than the tenet is covered in The Housing Benefit Regulations 2006. See the relevant section below:
http://www.legislatio...13/regulation/95/made
95.—(1) Subject to paragraph (2) and paragraph 8(4) of Schedule A1(1) (treatment of claims for housing benefit by refugees), a payment of rent allowance shall be made to a landlord (and in this regulation the “landlord” includes a person to whom rent is payable by the person entitled to that allowance)—(a)where under Regulations made under the Administration Act an amount of income support or a jobseeker’s allowance payable to the claimant or his partner is being paid direct to the landlord; or
(b)where sub-paragraph (a) does not apply and the person is in arrears of an amount equivalent to 8 weeks or more of the amount he is liable to pay his landlord as rent, except where it is in the overriding interest of the claimant not to make direct payments to the landlord.
I think you may well lose 8 weeks of rent but hopefully you can limit your losses there - good luck with your sale and evicting the present occupants
IggyB