I think the above point by Jamanek regarding re-sale of the car is an important one.
Most of us when we buy a car we don’t think enough about the ability to sell it a later point. I ,for one, was smitten by my car when i first saw it, and pledged that i will keep it for life and never ever sell it ! and yet twelve months after buying it I have come very close to selling it many times, after it developed numerous problem.
The reality is that you might need to sell the car because you need the cash urgently, or the car develops a major problem that costs more to fix than the value of the car (this CAN happen, for example if the Auto transmission seized, engine head blows etc).
Its at that point that it becomes MUCH easier to sell a merc with 100k miles than one with 300k miles, regardless of how well both cars has been looked after.
Bearing this in mind , £6000 is definitely alot of money for this car, even though i accept the arguments that the Turbo Diesel mercs are solid work horses etc. At the end of the day, its a question of how much its worth !