[Beejay]

Update from the above. Just back from the dealer. I am emotionally drained. We were told a harrowing tale of how tough it is for car dealers, and how everybody is worried about their very existence.
Kidding of course.
The manager we talked to was adamant that the used car market was 'dead', and that we should consider ourselves 'lucky' to have only experienced a 20% reduction after four month. After we talked around the edges a bit and I asked how the gain for the dealership of $1500 now would sit with the loss of future business and referrals, he complained about being 'blackmailed' and bluntly suggested we sell the car privately if we're so convinced we're getting a rough deal from them.
Looks like we're going to take him up on that suggestion. At least they don't get an overinflated gain from re-selling our current drive that way.
We're taking delivery of the new one on Wednesday, so will look to shed the old one pretty quickly.