I often say (especially to a husband and wife team or a team of 3 or more buyers) when they start finding tiny scratches that we'll kindly knock off £100 for every scratch mark they find. Quickly they reach the magic figure of £500 which I then deduct from the original list price when NEW (printed on the CAP or Glass valuation part of the HPI Report) and inevitably our car is still a lot lot cheaper. We all have a little laugh reminding each other that we are not looking at a new car and more often than not this works and we still have a deal. The customers get a box of chocolates rather than £500 off and still leave quite pleased.