I sold my GF's 2005 Corsa recently. Wasn't in mint condition, above average mileage, part service history, put it on Autotrader online for £2,350, which was £100 above the 'Private Sale' figure on the Parkers SMS valuation service.
Sold to the first viewer 2 days after the ad went up, 2nd phone call, for £2,200.
Told him it'd never been in accident, all original panels etc..
What he didn't ask was if it'd had any mechanical failure - the Camshaft had literally snapped TWICE in 2 years (manufacturing fault that VX won't take responsibility for), so it was a ticking time bomb. But he didn't ask.
We'd been offered as low as £1,200 Part-Ex at Ford, would have been happy with £1,800 private sale bearing in mind the history, so were made up when we got £2,200. Guess you have to ask the right questions - often 'no accidents' is true but it should lead you to digging a bit deeper.... death rattle springs to mind here.
It's great what a valet and a clean engine bay can do for a sale.