They do have a bit more then just rebadging them in some cases. Vauxhall/Opel, for example, gets the base chassis and body and finished manufacturing the the rest of the vehicle to fit UK specs (the hardest in Europe). The European line of Isuzu's (the Rodeo and Amigo, known as the Frontera and Frontera Sport) have different features then the rest of the world. The 2nd gen Trooper wasn't rebadged for the UK and is sold under the Isuzu name.
Here's pics of the UK Frontera Sport for example. They came up with different tail lights, bumper, headlights, brush guard, roof bars, and a completely different hard top setup with removable windows and top roof portion. All of this is Vauxhall/Opel factory!

And on a 'this just doesn't make sense' side. The UK/most of Europe requires side marker turn signals, as does Japan. So the Japanese Isuzu Wizard/MU have sidemarker lights installed on the front fenders between the corner light and the wheel well. Instead of using those on the European models, they installed the sidemarker on their models between the wheel well and the door. Yet another item that makes the Vauxhall/Opel versions of the Isuzus unlike any others.