Personally i think 3k is a bit of large mark up, but i appreciate you point.
Example, i sold my 04 JCW Cooper back to BMW dealer as i couldnt be arsed with a private sale, i got back just over 10k for car. Its just gone back out from the dealer for £11750. Mini's have the best residuals bar none in UK car market at moment on a percentage basis (ignoring recent Caterham claims for point).
That doesnt change fact though UK cars are beginning to trade hands at ever decreasing prices. Heck a member on here got a 04 GT uk car for £16750.
The cars are out there, and assuming everything about them checks out, then bargains are to be had!
If someone is willing to pay £19k for a car that can, with patience potentially be found for £17k then fair play to them. Each to their own. Its what makes a world a unique place. Everyone wants to sell for as much as they can, and buy for as little