I would like to vouch for DTD too, ordered my current GTI through them in 2014 and due to pick my new R up on Friday through DTD again. Always found DTD really helpful and the dealers have been good too, the dealers have been different each time but they seem to have someone just dealing with DTD orders.
I suppose the downside is the location might involve some travel for you if you want to pick the car up. Orange Wheels are good too and they will part ex, saying that the quote I had from their Audi dealer for partex was poor.
The VW is taking my GTI this time though and offered a fair price so sorted.