I wrote a couple of days ago about insurance in California v Northern Ireland.
One important difference - a consequence of how different people have different limits of third party liability - is that your insurance company really, really wouldn't want you to tell the other party in an accident what the limits of your liability is.
The question doesn't arise in NI.
I note at this point that drivers in California are far more civilised on average than drivers in NI. (Who are sometimes f***ing insane.) It's probably cultural, a product of the cold northern climate or something.