Google New Immigrant Insurance. I do not know of any I would recommend but either that or take the risk.
I have been out of the biz for a long time and there certainly not anything in the UK back then, not an obvious market for a UK Insurer but who knows now.
Thee is Global Insurance, I seem to remember CIGNA was at least one insurer who did it aimed at the Global Senior Exec market, seems overkill for this.