You may have to get storage built. my Great Aunt has had alcove cupboards built eveywhere she can. A big slide robe in the small bedroom that is sectioned so she can put the hoover upright and store other tall bits, a small clothes rack, lots or drawers and shelves. She hates slide robes but it seemed the best solution and now she really likes it.
We are currently decorating our house to get ready to sell for the New year and downsize in the summer and I'm being totally ruthless with my stuff . My tip would be to get stuff out of the house quickly, don't leave it in the hall waiting to give it to the "right" home or charity shop, just get it out. That might mean putting good clothes in a clothes recycle bin in a carpark rather than donating to a favoured charity shop that restricts amount of donations or has parking restrictions. Just get it out. We have also sold stuff on gumtree incredibly cheaply for collection only. Once it's gone you realise you didn't need it anymore.
I had a massive amount of kitchen kit with loads of doubles and devices I rarely use (like a food processor, liquidiser etc. I mainly use a stick blender and like to chop things). There used to be up to 8 people living here but now there are just five and hopefully 3 when we downsize so I'm getting rid of all gadgets that haven't been used recently and doubles as well as my huge pans.
I finally managed to persuade my P to get rid of shelves of books (just keep the "precious" ones). We used to have 4 floor to ceiling dust attracters in the living room. We now just have 1 glass fronted cabinet. The room looks huge and clean, sneezing and cleaning down. I sold a load of the books (and computer games/dvd's)to sites like webuybooks who send a to courier collect them. The rest went to charity shops or the recycle bin. I've culled the bedding and towels down to one on the bed and a spare.(local pdsa got the towels) I've vacuum bag packed some bulky coats and the spare duvet and put in a big drawer that runs the length of the bed (the bags might fail but it gets them in under).
I did one room at a time. not the Marie Knodo method of gathering all one type of thing together. Now, I often see something and think I don't need that and it goes in the basket I keep in the hall for charity shop stuff. I also enforce if I want to get something new then something has to go.
The downside is now that the house looks so fab it makes me very sad to have to leave! Good luck x