Be clear about your mum's opposition to all help offered because she has lost capacity and is unable to understand her needs. Point out it's really not going to help if they go to assess your mum and just ask what she needs. Also tell them of your plans to replace her tatty stuff, get her new clothes, etc and the opposition you are getting from your brother even over these simple things.
Take some photos of mouse droppings, your mum looking a bit unkempt, etc.
Take some photos of mouse droppings, your mum looking a bit unkempt, etc.