Take a look on the GolfMk8 forum, (not helpful but) some private buyers have been waiting 2 years for a GTD, you want to chase your dealer to see if there are any stock vehicles as the Golf 8.5 will be along soon. At least chase them for an update i’ve been updated monthly so far. It takes them a couple of minutes to respond to an email or give you a call.
I placed an order for an R-line end of October and been told Build week 6 for mine (this could change though) its best to keep yourself updated with the facelift coming too.