Law has changed now stanley man - its not fit for it spurpose anymore, its fit for all its purposes - due to advent of seconhand sales of items - items may still be fit for one of its purposes, but not all.
As a rule of thumb, a registered trader has a legal obligation to let the prospective purchaser know about any previous damage or financial incumbrances on the vehicle, but private sellers are only under this obligation if they are asked if there is any by the prospective purchaser.
I do know that trading standards do like to get involved if a substandard car is sold and it subsequently causes an accident.
I take it you can't find this guy now anyway?? - Just take it as a lesson learned and bite the bullet.