If he has said she has capacity, could your mum sign a letter of permission to the doctor, that you would write, giving them permission to give you access to her medical records and to act on her behalf and get the nursing home manager to witness it?
I know it's not a health and welfare PoA but establishing capacity with the least further cost, this may or may not work.
I can only tell you that my mum's doctors are wonderful, I didn't realise how much, mum gave them permission only verbally years ago to discuss everything with me. The recorded it on her notes, they are open about everything, I even had an appointment on Monday for a medication check, she'd forgotten what she should be taking, and new prescriptions were printed without mum even being there.
The GP is grateful that I can remember what was changed and why, who did what, how her health is deteriorating but she did give permission when well. They just tell me the lot no Health and Welfare PoA needed.
It depends on the GP and I've been taking mum there for 20 years so they know I've always known about her conditions. Maybe just lucky they are so kind.
