Ive just put a pair of part worns on the 306, first set ive bought. I understand they typically come from germany where they have far stricter rules on what can or cannot be used. Some scrap yards only sell the part-worns that come in on cars, others do a trade in imported part worns too.
They way I look at it is, you would have no quarms running a second hand car on the tyres it came with having had a look over them, whats diffrent in a part worn bought tyre only?
I would rather have a decent brand of nearly new part worn, than a brand new chinese ditch finder which will be 'part worn' after a weeks use anyway. The part worns ive just had fitted are that good you would stuggle to tell them from new bar the lack of moulding marks on the tread.
Daniel