Can someone explain to me what the grounds would be for a complaint to the Financial Regulator? From my understanding financial institutions can charge what they like as their variable rate regardless of what the ECB / US rates are.
As many of the banks have been 'bailed-out' by the government, there is currently political leverage on banks to reduce rates when ECB goes down to give the impression that they government actions are all in the best interest of the consumer. This does not make it a regulatory requirement.
If you think you are paying too high a interest rate, then shop around and move your mortgage business.