Cheers for that Kempie.
As it's an Opel, it is presumably a European import (tend to come in from Cyprus a lot for some reason?).
We have quite a few European (parallel) imports on cover, and quite honestly, I cannot say it's ever been an issue if it's been insured as a Vauxhall rather than an Opel. This is from our Underwriting intranet site:
"EU imports should continue to be coded as imports only if there is already an existing import code on the vehicle list. There is no requirement to refer these cars to UW as the UK equivalent code can be used if and only if it is an EU manufactured car and there is no import code available."
Basically, it makes no difference. So long as it is right-hand drive, then it should technically be treated as a UK spec model.
Not sure if this vaires insurer to insurer, and whilst I completely agree with Kempie's worst case scenarios, I would doubt that anything worse that reclaiming the difefrence in premium would actually happen.