I was going on the presumption that the manual was under the 150 threshold before the configurator for the gti was taken offline and now it's over the threshold now it's back online.
I am sure the manual used to be 148g/km but the new WLTP tests cane manuals because of the way they test them, whereas DSG can be gamed a little (yes, we're back to manufacturers playing around for test conditions... not just for testing, but definitely setting things up for test passing).
I should think you feel a bit annoyed about that, but in theory the price you've agreed is an on the road price, so it shouldn't make you out of pocket.
Plus, the extra cost for DSG still isn't offset by the road tax savings in year one...