I didn't ask for a discount but I got a good deal on my partex - In effect, they gave me the car's "value" as the part exchange element then bunged another 1/3 in as dealer's contribution. In addition, I would get another £738 thrown in if I use their finance deal. I worked it out that with a decent deposit - £10000 or so, the extra cost of finance over two years is wiped out by the £738. Then you the have the option of paying the loan off after a couple of payments, so it's a bit of a no-brainer. However, if you keep on paying monthly, you're quids in at the end - inflation reduces the effective cost of the payments plus you keep more of your money in the bank earning interest. Even with low inflation and interest rates, it's still worthwhile.
It's the bottom line that matters though ! I have the feeling that there is a VAT benefit if they give you over the odds for the partex and "discount" the price of the new car.
Have you been driving the same X Type for 14 years ? If so, what mileage and did you have any problems with it ? I sold mine at 80,000 miles after 6 years.
Ian