I hope I got a good deal.
I think in the cotext of the very low mileage yes you certainly did. If it had a couple of thousand on it I would be less inclined to agree.
Looking at the alternative - if you had ordered this car new (as specced) it would come in at £34,580. You would be able to obtain a 12% dicount by using a broker and this would have resulted in £4,149 off the price.
As you got an additional £1,800 off then yes, thats a result - although only if the car truly reflects the spec you want as at £28,700 or thereabouts its still a very expensive car!
As an aside (well more of a theory really), if you were happy to have the retro cloth interior (I personally love it over the hugely over inflated cost 'Vienna leather'), the list price would then be £32,880. Ordering a new one, with the 12% discount, would result in a price of £28,934 - just a liitle more than you paid for the pre-registered/slightly used demo (with leather)!
Of course you would have a four month or so wait on your hands (not to everyones taste!) so all in all I guess most people would be happy with your purchase - but you are the one who needs to be happy and it does not make a big difference what we say!
Wish you safe and happy driving :-)