Surely you can check any standing orders or direct debits by looking at previous bank statements.
I suspect you are in a similar position as I was a few years ago, looking after my late mother’s finances. I had sole lasting power of attorneys (financial & welfare) – but managed to get by without ever submitting either to an official body/organisation.
I wrote out her cheques for household bills – all she had to do was sign them; towards the end I wondered if some might be rejected due to the strange signature.
I had her bankcard and knew the pin number, using this to withdraw cash for her shopping and other sundry items/expenses.