Once the build week is confirmed there is not a hope of changing or adding the spec. Surely if the dealer could add the wheels he would..........why question it?
My dealer is a real genuine guy and I get on with him well, besides I have a mate who works at my dealers and Im sure if he could do something he would, like you say he would if he could...Marc(my dealer) said that there might be a possibility to swap wheels if there is another gtd in the local area at the time mine gets to them....I will just have to wait and see, but like already said I'm more than happy with my spec, it was just an after thought...
Steve