Autism Social Housing improvement needs

As so often, a system is too inflexible, but nobody within it will alter it.  Therefore this would need lateral thinking.
Two prongs would seem useful.  A) Find someone  powerful who can persuade someone at the head of the obdurate system to make a non- routine solution Find someone powerful who can present a watertight case.

This is luckily bang up your street.  Think around who you know professionally, whose qualifications and reputation are too towering for any council employee to sneer at, and persuade them to lend their agreement to your  schedule describing  the necessary work.  That would make it impossible for anyone to say " only council employees are able to know what to do".     Then, get pricings from reputable builders who would carry out the work (ideally, ones who already are on your own or another council's approved  list,  or in some other way cannot be called cowboys about to wreck council property)    Then try hard to find examples of  comparable work already completed, and discover what it cost, both privately and to your own or some other council, to be able to offer evidence that what you propose is not only the right and necessary thing to do, but the price and the standard will be favourable in comparison with the council's own proposals.

A) Will be the usual suspects, of M.P and councillors, but they will have a deluge of damp complaints to forward to the council.  You don't seem to have mentioned your mother's asthma to the council, but hundreds of other damp sufferers  will have added doctor's reports of asthma to theirs, so don't be left behind.  Others will have photos of black mould (carcinogenic) which they do not remove as you do, but photograph.   The falling plaster is your evidence, but you need to take care it is not unjustly used as a weapon against you, because the habit of long showers is ' harmful activities by tenant'. 

 (On that point, the first thing would be a more effective extractor fan.  You could easily find whatever is the world's most powerful bathroom ventilation! Actually, there might be mileage in using your professional status plus your siblings' exceptional needs, to get a manufacturer interested  in supplying it at reduced cost , in return for the commercial advantage of your story. You presumably measure the water vapour levels in the house? Photos, before and after moisture measurements, and your professionally written  favourable report would be a convincing sales advantage to them.  You could replace that at your own cost and the council could not reasonably hold it against you, even if you do it without getting consent first, provided of course you kept proof that a qualified electrician had done the work, and photos and other  proof that the making-good is carried out "in a workmanlike manner" to restore the appearance to as good as or better than before.)

Presumably you are in touch with whatever disability groups and autistic organisations and (for mum) asthma organisations may lend support ?   Ideally get a medical opinion from the autistic consultant to explain in words of one syllable why the siblings need these long shower routines. Need, repeat need, as a medical requirement, not just 'enjoy long showers' (which is what the council employees will think to themselves, when telling one another "some tenants won't ventilate their property and insist on  spreading wet washing everywhere, then complain of damp- and it is all their own fault").   Bear in mind that the council's systems, and staff, are designed to deal with people who wreck housing, and people whose cousin's mate can fix plumbing, so when you, sensibly, propose your "experienced professionals", the person behind the desk does not differentiate, but sticks to the safe old script of telling you to ask permission and automatically refusing.   And the automatic refusal  is what  brings you to the other option,  which may be available to your mother on legal aid, of using the "....such permission may not reasonably be withheld", which would apply to any landlord, but doubly so in cases involving disability.

Hi there 

Just to add have you been in touch with your local mp about this 

Unsuitable housing has been featured on the news quite a lot recently so it may be worth a letter or email to mp