ajmoir36: If you're looking to trade for a MK7, i'd ask myself why - the performance increases, the better ride/handling or the standard kit?
If you trade in a MK6 GTD for a MK7 GTD, the MK7 won't feel much faster (if at all), the refinement does take the edge of the perception of performance even though it will drive nicer. Going petrol to GTI/R is going to feel more different, different way of driving (although not as different as previous petrol variants are, considering the huge jump in torque on the GTI/R to almost GTD levels.
Your car is now old enough to be affordable to a great many people, but its also old enough for the VW dealerships not to be too interested in having it on their used forecourt - it may well be farmed out to auction. With all that in mind, you might get a very poor p/x price and you'd probably get more for it privately, and it shouldn't be as hard to sell privately as say an 18 month old MK7 GTI/GTD.
Before you do anything else you need to find out what the going rate for your current car is when sold privately and traded in (you might get less than £10k offered in p/x). If you sell privately you're in a far better position to chase broker sized discounts on a new one, or maybe you can scour the net for some good early MK7s - a fair few GTIs and GTDs are getting chopped in for Rs right now.