I suspect Southern are the only UK-based trust company recognised by the FAA. I know other UK-based US-registered aircraft are registered to trust companies in Delaware.

It appears that some of the Fighter Collection’s aircraft were owned by people such as John Crocker and Steve Hinton and operated by TFC while they were US registered; the Bearcat was owned by B&S Advertising until it became G-RUMM. The unfortunate Don Bullock A-26 was owned by Duane Egli.