Nightmare, my mechanic had this with some young lad, in the end he said 'keep it' but the next thing, a finance company got in touch saying they wanted to recover the car as payments had stopped.
My mechanic informed them they car would not be moving until his bill plus storage had been paid and he ended up buying it from them for peanuts. His misses has it and its been great for the last 4 years lol!!
I would say the guy is a chancer, the threat of legal proceedings may make him buck his ideas up.