I cared for my wife, who has Dementia, for three years before she was admitted to a care home and she got the discount, we were only charged as a single person living there (me), so 25% i believe.
Theres a lot more thats not readily known about too, PIP benefits, Home Care help and payments from the local authorities, every little bit help but you must either know about it before hand or be told about it, its just never advertised.