Following on from other threads, I thought it might be helpful to share our experiences to help those starting the PoA journey.
My dad still has capacity but Barclays Bank set me straight up with my own cards & PINs for his accounts once I had taken the certified copy in along with my ID (and my dad). Plusnet have done it over the phone. Both made it very straightforward. Plusnet have a scheme for customers needing more support, which I was impressed by.