Trading Standards Website:
"When you buy goods from a trader, you enter into a legally binding contract governed by the Sale
of Goods Act 1979, as amended by the Sale
and Supply of Goods Act 1994 and the Sale
and Supply of Goods to Consumers Regulations 2002.
If you buy a used car from a trader it must be of satisfactory quality, fit for the purpose, and as described. Obviously a very old car with a high mileage will not be as good as a newer car with a low mileage, but it should still be fit for use on the road, in a condition which reflects its age and price, and reliable.Traders cannot take away consumer's rights by using terms such as ‘sold as seen’.
Just as an aside, the term "sold as seen" means that they allowed you to inspect the vehicle, and that any faults present would have been obvious from this visual (seen) inspection, however if you were unable to "see" certain items (such as the clutch/gearbox) but had no reason to check these items as the garage told you that they had been replaced, then any fault with this is a misrepresentation on their part.
The only way they could avoid liability is if there was a long delay in you reporting this fault, and next day/nine miles doesn't even come close. They are just hoping that if they shout and fob you off enough you'll go away.
Could be an interesting Wiki meet, everyone down there telling their prospective customers what they are like when things go wrong, how long do you think we'd have to be there for ?