It does all seem a bit weird. I had to 'steal' my wife's NCB for my first Z as they wanted 3 years no claims to insure me, but I'd been in a company car. They just moved all 9 years to me - how does that work ? Meant that we got stiffed for a year on her car mind, then it dropped back by half. Now she's named driver in hers & building it back up, and I am the only driver on mine with 10yrs+. I guess my situation is slightly different though as both cars are daily drives, and the annual mileage on my policy - 15k - does most of the damage...
Oh and aero skirts are REALLY expensive to insure. Don't ever tell them you have them, because that crease down the middle of a bit of plastic can beggar you, on the off-chance an identical car parks next to yours, making yours more desirable to any thieves with a serious eye for detail that happen to be passing at that exact moment :x