It depends whether you are selling it on a cash purchase deal or an SOR deal. Bowler Automotive near Banbury charge £1500 plus VAT on an SOR deal and even that is negotiable as I know from a neighbour who sold his Porsche through them!
My McLaren has just gone to a Dealer on an SOR basis and the deal is more than that, but nowhere near the figures mentioned for cash purchases. I’ve had Morgan’s sold in the past by a Dealer on an SOR basis for circa £1200 including VAT and even less for my M3W!