i agree with everyone here.....1K tops.
Mileage is big, and Omegas will wear it well, history, is it dealers? if not then i would use that to knock him down.
Cam belt, rocker covers and the fact that the radio is not a gen vaux one, you have lost the screen display and the steering wheel controls, this may not be important but it helps from your part with negotiation.
If it was me i would shove a grand under his nose, hold my hand out and get him to shake on it, if he says no, the tell him the money is there for 7 days after that you will be off buying another that you know is coming on the market
Play then at their own game, they will hate you but you get the car you want at the price you want