Thats probably what you would get for it Private, but its the previous Leon so that also goes against it. Dealers would take it off you for that and sell it for £12000/£12500. I didn't think they would budge on the price for the
CTR, I know that the dealers I spoke with would only give discounts IF there was no part ex because if you part ex they then have to try and shift the car you've taken to them and there is no guarantees that it will be sold in a week or 20 weeks.
You'll probably find that the dealer will phone local Seat garages and see what they will take it off their hands for, but they usually offer less than what you have been offered from the dealer as a part ex. But I wouldn't be expecting anything near what you were expecting. I was offered £3k less than I actually got for my car.
I looked at a new Mini & a RX8 a few years back and was offered half the value of what other second hand Mini's were on the forecourt at and they had basic spec and more miles on the clock so I didn't even entertain them. The bloke from Mazda actaully confessed that they would take the car off me for the laughable price and put it on the market at double that and probably sell it in a week (as they were still really in demand at that point)
I do hope that they come back to you with a price nearer your expectations, have you thought abou sticking it on Auto Trader and seeing what interest you get?