As for parts quality, there is a way in between that works quite well in my opinion, which is to use trustable brands.
Example:
http://www.carparts4less.co.uk/suspension-arm-and-suspension-jointsI would mount both the Lemförder as well as the TRW part without a doubt.
I would not feel well using the no-name as well as Ocap part. They could be ok, but I do not know the brands and there is a lot of crap being offered on the market, so it's a gamble for me.
After all, the Ford OEM part will be produced by manufacturers like the first ones mentioned, not by Ford. (True, there are lots of anecdotes/rumours of different higher specs being used for OEM as opposed to aftermarket within the production at those manufacturers. These do sound plausible indeed, but until now I haven't had those brands failing on me, so still their aftermarket specs fit the bill, apparently).
Following this policy means your parts still cost twice as much as the cheapest offer available, but with the cheapest offer uncertainty will always ride on the passenger seat, apart from the time and hassle it takes to mount a part like a ball joint another time.
Just on the example of brake parts, I'd trust these manufacturers to be more or less equivalent to OEM:
Brembo, Ferodo, Judd, ATE, Textar, Nissen, Lucas, Bendix, Bosch, Valeo
I would use these brands if no better alternative was available:
Febi, ABS, Herth + Buss, Meyle
I would avoid these brands:
Unmarked Ebay stuff, Moog, Bölk, Eurobrake.
Keep in mind there are a lot more contenders in every category. At the same time, I have had Bosch brake pads fail badly on my Smart Roadster (a well known issue for the SR) and a have had Meyle suspension parts that were better than OEM. As always in life, the only certainties are death and taxes.
Take care, Kai
