Hello Treacle. My husband also has Lewy Body Dementia, but our reduction in Council Tax banding, is due to the fact that he will now be reliant on a wheelchair, and has a bedroom for his sole use.
Steve has been in hospital for 3 months, and hopefully will be discharged within the next 2 weeks.
Goldengirl, all councils should have the same rules as regards this benefit, as funding comes from the Govt. via the local authorities. (that's what the council fella told me yesterday when he visited our home).
He came to view the room my husband sleeps in, and said we qualified.