I believe that the wording in the Mental Health Act says that the wishes of the person have to be "taken into consideration", even if they have lost capacity - which is not quite the same as saying that they have the right of refusal.Whilst the LPA instructions point you to the mental health act which says that no matter what, the person still has the right of refusal - interpreting this clause with someone who has Alzheimer's is a very different ball game.
If they have not lost capacity then they do have the right to make "unwise decisions".
It hinges on whether or not they have the capacity to make that decision.
Edit to add - here is a link o the Mental Capacity Act code of practice, which is long, but you might find helpful, especially chapter 5 which talks about making decisions in their Best Interest
Mental Capacity Act Code of Practice
Code of practice giving guidance for decisions made under the Mental Capacity Act 2005.
www.gov.uk
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