My post seems to have been lost at the end of page 1, so I am repeating the saliant points.
I traded my GTD last January and broke even on my PCP, after about 2 years (GFV £13,225, settlement £15,319). Given my figures, above, I can see your point. Seeing that your deal was done around the same time as mine (March 2014), it is difficult to imagine why the 2 GFVs should be over £2K different! Hope you manage to negotiate a deal.
So can anyone else, who started a PCP on a GTD around that time, show any figures, so that we can establish a norm?