SDP on ESA if cl in rent-a-room scheme

Hi, having problems finding regulations for the following circumstance, to quote in an appeal.
Cl gets PIP ER DL & Mob and IR-ESA Support as a single claimant. He lives with his landlady under the rent-a-room scheme, so pays commercial rent, but he shares the living room, bathroom and kitchen with her.  His rent includes heating, lighting and CT.  The landlady isn’t a relative.  She cares for him but isn’t eligible for CA so I told him to try for SDP on ESA as the DRH indicated he should be counted as living alone.  This has been refused, at MR stage, on the grounds that the tenancy agreement says he has the ‘run of the house’, that his landlady is his carer and mentions she has no tax liability (this is because it’s a rent-a-room scheme).  I’ve told him to register an appeal anyway but wish to supply further reasons.  I would be grateful for any info.

Have a gander at this; it’s not been amended since the introduction of the scheme.

http://www.legislation.gov.uk/uksi/2008/794/regulation/71/made