I bought the D80 with the 18-70mm lens because it had much better reviews than the 18-135mm lens and has a metal bayonet. I then bought the 70-300mm VR lens in addition. For about the same money you can buy a D80 body and the 18-200mm VR lens. I believe there's one in stock at ffordes
for £549.99. I've bought from them before with no problem. I reckon you'd get no more than £100 or so if you traded in the 18-70mm lens at a camera shop. You'd get more if you sold it privately. ffordes have had them on sale second hand in the past for between £150 and £180 so will have been wanting to make a profit on that.