You could always submit a PACCC application claiming hardship and discrimination under the equality act 2010. Since this act replaced the disability discrimination act it has become much more far reaching and many of the military get out clauses have been removed, I suggest a good look through ref married vs single.
The template for the application is contained in both 752 and 754. Fill it in with as much detail and supporting evidence as you can. For example projected cost of moving vs projected cost of not moving and living in. If he is likely to be disadvantaged by having to sell (ie negative equity or mortgage fees).
Once complete it needs to be submitted to your unit admin who will write an accompanying letter either supporting it or not supporting it. It is then sent to SPVA. You have 2 appeals if it doesn't go your way.
It is essential that you indicate what entitlement you are seeking. It is not a whinge about the posting but you want exemption from paying accommodation charges as per married personnel because you are required to maintain your home. It shouldn't in the eyes of the law matter if you are married or not.