It's my understanding that if you buy a car from a trader it has to be fit for purpose for x amount of time after the sale, so he would have some degree of come-back. However I believe that come-back is with YOU, not whoever he wants to take it to - I think he might have kicked himself in the nuts with that as he hasn't given you the chance to fix it.

Dan who works here knows better details than me, I'll ask him when he gets in tomorrow.