The price is good, the only thing that may happen is private sellers in January will reduce their prices to something realistic, once they see that their car is not selling at all (as you've seen the traders are starting to do this, just to shift the cars on).
I don't think that the registration year will make much difference by the time you come to sell it, I presume you'll be keeping it for a few years and its mielage and condition will be far more important than a technicality like that.
Without keeping going back to the heated seats, I do think you instantly reduce your potential market by 50% by not having them, plus it may spoil your use of the car too - there are plenty cracking winter days to get the roof down but it's far more pleasurable with heated seats, and if you take the Mrs with you then it might mean the difference between having the roof up or down.
Why, for the sake of a few hundred quid, people don't spec them in the first place I have no idea :scratchhead: