many thanks
ended up using a tweaked version of the final demand template (using the word fiduciary in two letters would have been excessive) with an addition at start:
In response to your letter offering £80 as a goodwill gesture - your offer is accepted only as partial repayment of the outstanding balance and i do not recognise it as
full and final settlement of my complaint. I also do not recognise your statement that "future valid charges will stand". This is because I am aware your current charging structure is unlawful.
capital one initial request for repayment went off today as well.
good luck to all
take care