I have the same problem. I've a perfectly good car (Y reg IS200 SE Auto with a few signs of ageing, especially the alloys, but otherwise in good knick) that the wife is making me get shot of because it's "too expensive" and "not suitable for the family". Had her (the car that is) from new and it's a painful thought of having to sell a car that's perfectly good and will be more reliable that the crud my wife has (i.e. a Renault Scenic!). Trying to delay the inevitable, but suppose it's getting to the point where it's either the car or the wife.
I saw a suggestion on here that eBay may be a good option to get a decent return. I did try a couple of garages, etc. and I nearly cried when they told me how much I'd probably get for it. Certainly no use for trading in for something else as I'm skint. I'm sure that if I had the means I could strip her down and sell the parts, but don't have the knowledge or time to do this. Does anyone have any other suggestions on how best to get a decent sale?