The Volvo shop I deal with typically stocks OEM parts, which isn't cheap.
They sell the OEM parts for a little less than a Volvo dealership. They are
an independent shop.
Most shops make their money by selling parts. Some shops use good stuff.
Most of the places I've dealt with use good quality parts, because they
don't want to see you back for repeat/free/warranty work. However, you're
right, you never know.
I don't know what a Chinese timing belt looks like, my car has a chain 
..
(B280F and still running strong after 300K kms!)
