This is sort of what I was referring to in my earlier post.
There is something whereby a property can be declared unfit for human habitation, but this seems only to apply to rented property. I dont know what happens with homes that are owned, though think there is some scope for council intervention if things are awful.
(I too watch too many C5 documentaries. Indeed one of my secret desires is to change the channel on my mums TV. She can only turn it on and off, and believes she is watching SKY (because she can afford it, and for a very long time we could not so it was one-up-man-ship) but in fact watches BBC1. I like to wonder if she would notice if instead she spent her life watching C5.)
Anyway back to topic. Many Councils have someone responsible for Private Housing within the housing department, though the job and title might be more focussed on private rentals. If you can find the right person. probably via the switchboard, and if you can email photos, they may have ideas of what can be done to prevent her returning on the basis that no one, whether vulnerable or not, should be living there. This in turn will force the hand of both social services and the hospital and, in effect, your mother. Shelter may also have some advice.
I appreciate your mother has some serious alcohol/MH isses and has withdrawn, but once my mother gave up the fight to remain independent she has been so much better physically and mentally. In lucid moments she will confess how grim it was on her own with no working oven, heating and more. A good cooked lunch, helpful people at reception, a handyman, and indeed film night on Wednesdays, has reallyhelped her well-being. .
Most of us have not been able to do anything till there was a crisis. You now have your crisis, which is a chance to make sure she gets the helpn she needs whether she wants it or not. Getting the house effectively condemned is a bit nuclear, but perhaps that is what you need.
(FWIW from what you have said, the house is an auction job anyway and needs complete gutting, so you should not be reducing the value.)