Run an HPI check if you're serious. That will show up any issues such as stolen/recovered, outstanding finance etc. But I'd want the V.I.N, and reg,
and sight of the V5C. Remember that the V5C will be changing soon, as so many were stolen & used to shift cloned cars.
Once you have reg & V.I.N I'd ring a vw dealer, they would be able to tell you any warranty work authorised & carried out by VW UK. I'm sure they will also explain that a car on the written off register sure as hell won't be covered by a VW warranty, whether it's Cat B or D. You can also establish history by phoning the previous recorded keeper on the V5C (if there is one). In my experience, most are happy to give you 5 minutes of their time to tell you about their old motor.
If it's priced like that for an 08, there's a problem. I wouldn't p**s on it if it was on fire. Fleabay hides a multitude of bottom feeding low lifes. This guy may not be one, but it doesn't look or feel right.
As these boys say, Cat B is not for repair. This is