You sure? The fact that you gave him the car to use for 12 months negates the criminal act of theft. You'd probably only have civil action against him and the person buying the car could get him done for fraud.
The stolen and "receiving stolen goods" was recently covered in this thread
http://www.cableforum.co.uk/board/11...ters-59-a.html
Selling something you do not own might be fraud but not necessarily theft