I'd be focussing on the Group CEO and if that meant the US then so be it.
I had an issue with the 7 day insurance offer from HPI (since Aviva have stopped doing it, Swinton has only been a farce in my experience), so constructively wrote to the CEO of the holding company in the US.
I had a response from him within half an hour and subsequently the MD of HPI here and a call from his head of operations. They value constructive feedback and will usually help.
When Roger Davis was head of the retail banking arm of Barclays many years ago I delivered some well worded customer feedback directly to him by email and received a call from him the same morning with excellent follow up too.
I also went to the Chairs office at BT when my ex-Wife (who worked for them) had my phone line terminated during a spate of divorce proceedings unpleasantness - often going to the top is far more effective than fighting with 'Customer Service'.