Maybe a long shot but has any TDI owner here managed or attempted to obtain a CoC from VW?
My Dad had a late 2011 Golf which is well maintained but will be hit with the expanded ULEZ charge, TfL have said his car could be ok but he needs a CoC from VW.
He approached the dealer he bought the car from new but they didn't want to know, then he ran VW at MK but again they don't seem interested.
I've looked online and many manufactures seem to offer to provide a CoC for about £200! but no where can I find it for VW.
As a last resort I might try emailing VW Germany to see if I get anywhere.