Yep, afraid so. For me it's going back five years so the bad memories are fading, but I really sympathise. I found some branches of bank/financial institutions to be very helpful about these type of situations and others who just couldn't seem to grasp what you're talking about. It certainly caused me a lot of stress when I was trying to sort out my mum's finances, because I'd had to go down the deputyship route. There wasn't one member of staff across the board that knew what I was talking about re deputyship. The difference for me was that some people I spoke to went out of their way to find out what they needed to know so they could help me. Others would keep referring to power of attorney because that was something they knew about. 'No, I haven't got that, deputyship is completely different' (repeated ad finitum). I won't say which institutions I had problems with because, in my experience, however poor the training given in these matters, some people did their very best to help me (and succeeded) even though they hadn't initally heard of deputyship.
Unfortunately I'm sure your name needs to be on the chequebook. My deputy account, and thus the chequebooks, are under 'Mrs .... ...... deputy for Mrs ... ... ....', as is the debit card. I'm sorry you're having this extra stress on top of what you're already dealing with.