Well, its true enough if you buy the car at a knock down price, and plan on keeping it for a few years - then the adverse effect of partial service history on resale value will be lessened.
Its what could go wrong during that period, because
of the apparent lack of maintenance that would put me off.
Plus, it isn't really at a cheap enough price to tempt me.
What you also need to be wary of (as I presume you have a car already for trading in) is that they charge a high price for 'their' car, so they also give you a high value for yours. What you need to be aware of is the 'figure to change' (i.e. the difference in cost, that you have to pay).
Let me illustrate;
Dealer A has a car at £3500 values yours as £2000.
Dealer B has a car at £3100 values yours as £1800.
Dealer B is the 'better' option (assuming all things are equal) as the price you need to pay is £1300, rather than Dealer A's £1500.
Another fact that would put me off dealing with them in particular is the 'ding' in the door. Now these are relatively straightforward to repair (by people like myself), and the trade gets prices that the private individual wouldn't (not by me, I charge everyone the same
), but if they haven't fixed something so obvious (which would probably involve spending less than £50), then again, I'd question their integrity, and wonder how they could justify charging so much...
Don't fall in love with a car, buy the 'best' you can afford, that ticks most of your boxes.