Thanks for the responses so far. The faults ended up being the Turbo and alternator pulley (which had been sprayed with wd40 to hide the noise it was making), and brake pads and discs fitted incorrectly which made them dangerous.
We are going through small claims at the moment, and the seller has defended the case saying it was my responsibility to get it mechanically checked prior to sale (correct) and that there was nothing wrong with it (incorrect - engine management light came on when we drove the car away from the sellers house!!!). I have a letter from a local garage confirming the faults and existence of WD40, diagnostic reports, and text messages from the seller claiming it to have nothing mechanically wrong with it and be in fantastic condition (around 20 messages). I am aware that with used cars it is buyer beware, however according to citizens advice the sale of goods act covers used car sales from private if the car was misrepresented, which I'd suggest this was. The seller claims he said these things in good faith and he is not a mechanic. I know a barrister who has looked over it and said we have a reasonable case, but obviously it comes down to the court to decide and could go either way.
Oh, and the seller himself bought the car for 6000 and sold it to me for 3700 4 months later....
I'm just trying to get any additional available evidence to negate the need to go to court.
PS. In the 4 months he had it the seller did not need it serviced or MOT. I've called the garage he got it from and they said it was fine when they sold it to him. I have the full service history.