If your vehicle is not saleable, then there are plenty of scrap car processors who will dispose of your car for no fee. Make sure you choose an Authorised Treatment Facility (ATF), and that you obtain a Certificate of Destruction (COD) from them to enable you to cancel your road tax and vehicle registration from DVLC.

The official phrase for scrap cars is End of Life Vehicles (ELV).

Lots more information about recycling of individual components can be found at Waste Online.