Keep in mind that Sytner will want to sell the car on at a profit so expect to get around 10% less if you sell or trade it in with them compared to a private sale. That said there is less hassle and no doubts about their ability to pay and you may be willing to accept this as a trade off. The person to talk to at Sytner Nottingham is Ged Scanlon - telephone number (0115) 934 1414.
D3s are still very much in demand. The latest info I have is that Sytners only have around 7 new ones and 5 used ones in group stock. Since production has now ceased you should expect to get a decent price although a lot depends on age, mileage, condition etc.