Hi James, welcome to Sweden. I'm actually from Australia, have been here two years and will be for 1 more. Summer is pretty nice but just wait for the winter! Offset is the distance from the inside edge of the rim/wheel to the face that fits up against the hub/disc. Front wheel drive cars tend to have more offset (sit in further) than rear wheel drive. Fitting wheels with less offset will increase the track but the wheel bearings won't last so long. Going the other way you can run into trouble with clearance of the brakes, hoses and suspension components. Hope that gives you some idea.