[Tatsfield]

From whom is the warranty? If it is from a Volvo dealer and is the Selekt warranty, which is about the best second hand car warranty you can get, it is unlikely that an official Polestar upgrade would invalidate it. It's an approved Volvo option so an official Volvo warranty couldn't exclude it. And if it's not, as long as you didn't stick the Polestar badge on the tailgate, how would anyone other than a Volvo dealer with a diagnostics kit even know that the Polestar option was resident. It's not like it's a backstreet boy racer engine busting rewrite. Would it invalidate the warranty if you fitted an alternative set of genuine Volvo wheels with winter tyres? Of course it wouldn't. Seems like a restrictive practice to me and if you want the Polestar, I'd just go ahead and do it.