Please contact the Alzheimer's Society if you haven't already. Despite it's name, the Society helps people living with all kinds of dementia, and their carers.
Most areas in the country run Carer's courses for those looking after people living with this horrible disease. Do try to access one. I help to run them in our area and the people who come along say that they learn so much about coping, where to go for help, the different benefits available and about looking after themselves. Please message me if I can help.
Talking point on the Alzheimer's Society website is a brilliant suggestion Witzend.
It is an awful disease and, coincidentally, my DH's brother has been diagnosed with it.