Insurance for Non UK Resident son

Does anybody know a Company that will accept an additional driver who is non resident. The risk to the insurance Company is diminished and they have access to the UK resident owner and Main driver . Most Companies want to change an addition fee for temporary cover which is not much use as I never know when my son will fly in and want to borrow my car.

He was obviously UK resident once, has a full UK licence but now works overseas it seems our insurers put obstacles in the way of my adding him to my policy.

Does anybody have a similar problem solved?

Thanks