I managed to get this for my Dad because I worked in the field and knew what I was doing - you need to get yourself fully genned up as that is the only way forward. They back down pdq when faced with someone who challenges what they are saying. Unfortunately many of those doing the assessments have not been properly trained and say things that are quite simply wrong.
They also have a book for sale which I found was a really worthwhile investment. Once you have got a grip on the assessment criteria I would advise you to fill it in with your own assessment of your relative and be prepared to stand up and justify your assessment.
Also organisations like Age UK and Alzheimers Disease Society are good sources of advice. But it is a specialist area and even they sometimes get it wrong.
The problem of course is that the NHS cannot afford to provide all the continuing care payments that they are legally obliged to, so is always ready to try and wriggle out of it. It is a bit of a moral dilemma.
My BIL had continuing care for a good number of years which left him being cared for in his own home. My SIL filled in the gaps as she cared for him alongside the many professionals who came to their home. I believe the social worker was ace who worked closely with the health care team to accommodate all his needs. In the long run it was cheaper and more comfortable for my BIL to stay at home where he died peacefully rather than be admitted to hospital. So it can be done if the right people are heavily involved. Good luck to those who wish their loved one to stay at home during the end of life process.