Some even deliver on a trailer for free, so there's only a few miles on your car when you receive it.
I bought my 2018 Polo GTI+ through DTD and it was to be a fresh order. I was then put in touch with the supplying dealership contact, who let me know about a few "in the pipeline" cars coming through that would save me a lot of waiting, As it was, there was a car that I ended up grabbing, turning an 8 month wait into a 2 month wait. The car was trailered from Listers of Nuneaton to my place of work in Newcastle. The driver of the flatbed unloaded the car into the works car park and I went over it with a fine-toothed comb while he waited. The trailering of the car was included in the DTD price.
Went the same route to get the wife's car.
In both cases, I got rid of our would-be part-exes privately.
You don't generally get a good deal both ends of the transaction - great discount on the new one? Below par p/x usually means the hassle-free cost to change can be met by your local dealer. In my case, Listers were fine about taking my Golf R as p/x, but were up front that they'd only be offering £15500 (I got £17300 selling to a performance cars company just outside York, who had it up for £20k to sell. Your average VW dealer wants 20-25% margin in your p/x.