It appears that money is the issue and the landlord doesn't help ... having spent more years than I can remember installing adaptions an aids for the vulnerable and disabled, sadly your story is quite common.
My position was funded by Local councils, Social Services, and the Police. I had the luxury of a credit card with a very high limit and when I came across anyone in you position, I could just spend as much as was needed to rectify the situation, there and then .. then just walk away without charging and forget about it. The other alternative was I advise that a Social worker get involved or refer it to a colleague/case worker who would arrange for a visit to go through the possibilities. If you have little or no spare cash that is often the best position to be in when asking for support. If adaptions are required an Occupational Therapist would get involved and along with the case worker, they would find the funding for the adaption. I know you said the Landlord is against any building works... but I wish I could tell you how many changed their minds once they found they were getting a new bathrom for free. As a rule if the Landlord allowed the adaptions, the only contribution he had to make was for the slightly better spec, tiles or floor covering he wanted instead of the standard issue supplied.
Another point most people are unaware of ... depending on what trade or what employer you may have spent your earlier life with, their are thousands of long standing benevolent funds that help with these situations. The best one I ever seen was when I visited a 97 year old ex fireman to do a plumbing repair.. when I seen the condition of his bathroom I advised our caseworker who then contacted the Firemans benevolent fund.. they asked how much to sort the bathroom out. We said at least £12k .. they said 'Make it a bit nicer than the standard spec'.. and gave us £12k. If your landlord thought he was getting a £10k bathroom for free, all af a sudden he will forget about upheaval.
One more point I should mention before I go .. the best place for getting support in this situation .. if you qualify, is from SAFA .. if you served in the forces, even for one day, they will definitely help... Good luck.
Got to dash, there's a pint with my name on it waiting for me !