A good point, Graham. This motor insurance thing can be a bit of a bu***r, even in the UK.
My daughter, living in Dubai, wants to buy a car in the UK as she has a house there & her daughter is at boarding school. She can't get permanent motor insurance in the UK without becoming resident again, even though she was born & grew up there & passed her driving test there. Becoming a resident would not, however, be comfortable from a UK tax point of view. As a result, she's continuing to rent cars each time she or her husband go to Blighty.
Interesting you should mention 15 years of licence at no cost. Most of us 'poms' have never heard of 'driving licence' birthdays, since in the UK your licence used to be issued up until you were 70, and technically still is, though you have to renew your photo periodically these days. As I'm just coming up to such a birthday, my brother used the term & I'd never heard it before that. Is it every ten years or just five that count as being driving-licence events?