The ad is a bit misleading, Cat D is not defined by a little bump on the front. If its hit something then chassis and suspension checks would be a first port of call.
If he bought it damaged then he should also have taken photos of it, or at least have photos of when it was advertised as written off. Check also how long he owned the car, if its a few months it could be he buys up cars, quick fix, sells on.
Oh and the Nismo badge adds £10 value to it (or whatever chinese badges go for nowadays on ebay!)