On the off chance that this may help someone else, I complained to my bank about unfair packaged account charges (they had told me years ago that it was the only account available to me due to lack of credit score history and that it would improve my rating) and they basically told me that I had no case at all and everything had been legit.
I was unhappy with being fobbed off so wrote to the Financial Ombudsman, they gave me a form to fill out and asked for any correspondence I had which I provided. They said it can take up to 12 months to get a reply.
That was about 3 months ago and now out of the blue I have had a letter from the FOS saying that before they have actually looked into the case they contacted Natwest and informed them I had taken things further and that if I will agree to drop the matter they will pay the £800 in fees back and £700 of interest. Success!
I hope someone else feels spurred on too.