On the partner issue, if Paul Stagg and Commissioner Edward Jacobs are correct about retrospectivity and in addition if Paul Stagg is correct about the proper construction of Reg 101 in respect of partners, you are right: the partner is, according to Paul’s interpretation, a prescribed person from whom the overpayment is recoverable in any case where they were there at the time when benefit was paid (see the version of Reg 101 in force between October 01 and April 06). In his view, it is only the method of recovery by deduction that is limited to cases where the claimant and partner remain a couple. You can still recover from the partner by other methods.
Andy’s note of caution about contrivance is an important one. You need to choose your words very carefully. Deciding whether a tenancy was created to take advantage of the HB scheme is not generally the kind of thing you can change your mind about later. If you decided to award HB without having been told something important, and that information has now come to light, you may be able to revise your past decisions for ignorance of a material fact. Had you known that information at the time, what decision would you have made? If HB would have been refused, what would have been the grounds? That’s the way to approach it.
Sorry if this sounds like a late challenge for the pedant of the year award, but to say an overpayment has been raised because of a contrived tenancy is to leave yourself vulnerable to about half a dozen appeal tactics attacking the validity of your decision.