Sold the S-Max via WBAC, late last year.
They knocked us down £75 per wheel on the state of the alloys (which we expected - just not that much!).
Including the reductions, they offered about £100 less than the highest bid it received on ebay. I haggled and we split the difference, so I ended up just £50 less than the proce that it didn't sell for on the bay...
Ohhh, and they failed to spot the holed exhaust pipe that I had patched and that wasn't about to get through the iminent MoT
So, all in all, getting rid of a 2nd hand car is always painful, but provided you've already faced up to the fact that it's worth bugger all, then WBAC kind of gets the job done