I exercised my Option for exactly that reason... posted down to London and expected to pay full living in charges as I'm a 'singlie' - only living with my partner. I'm not spending life miserable in the mess Mon-Fri when I have a home elsewhere. It felt like 'constructive dismissal' as there was no other option other than leave.
Playing devil's advocate, has this ever been subject to a formal challenge? Over the course of a typical tour, Grade 1 accommodation would leave a singly almost 5K down compared to a married colleague in the otherwise identical situation. If not legally dubious, it is certainly morally dubious.