Only consolation is to imagine a German (other nationalities are available) motorist, driving a pre 2006 car, visiting UK, and trying to avoid paying CAZ or ULEZ!Good news from Germany! If you need a green plakette for your A2 1.2Tdi, you can send your V5 and CoC (originals) to TUV Bamberg and they will give you a D4 certificate and a green plakette. Cost is €80.
Before I had received the email from Herr Kestel, I had made an application to Berlin for a green plakette. All that they asked for was a registration document or a CoC. I sent them the V5 only, which shows emission levels and obviously no German taxation class. Cost is €6. This should be enough for a green plakette. If not, I'll have to take the Bamberg route.