After having sold all the bits that came off my car I was recommended this site to save delivery costs on......very easy to follow and will use your local delivery firms anyway at half the cost....just make sure you know the weight!
http://www.parcel2go.com/Quote-page....&col=214&qty=1
also means you don't have to wait in a long queue behind loadsa OAP's getting their pensions in the post office!