HB/CTR and ESA Better off

I am looking at appealing a HB/CTR claim.
Fact:
Mr & Mrs make a claim
Claim made in Mr name - Mr was on ESA WRAG and DLA MRC - Mrs - working
HB/CTR assessed using Couple rate and ESA WRAG component
Visit to client - Identified that if Mrs claims - would be better off as would be Couple Rate and Disability Premium.
Letter to LA to swop claimant and partner due to better off
LA asked for new form - paid from Monday following request to swop NOT from when better off.
They admit that they failed to identify better off calculation.

I have asked for Appeal - They arguing that as A11/2008 - is only guidance and ‘good practice’ they don’t have to follow it.

Any help would be appreciated.

Problem is that any claim by the original partner can only be backdated one month max and cannot in any case overlap with the original award. DHP is the only solution I can see and the Tribunal has no jurisdiction over that.

The circular’s advice to councils was pretty clear:
“57 If you receive a HB/CTB claim for a couple, only one of whom is an ESA customer, you should consider whether they would be better off if the other member of the couple were to claim HB/CTB and advise them accordingly.”

Where there is a failure to follow good practice, leading to a quantifiable loss of benefit income, it might be worth a complaint? The LGO site has various general info on complaint remedies, e.g. this pdf.