We have genuinely not had anyone complain, if there was then I would take it up with Whiteline. As I mentioned we have sold hundreds of sets as have Abbey Motorsport.
They are not a rose jointed link they are a sealed ball joint so are more than suitable for UK roads, if grease is applied to the threaded part at the time of fitting then adjustment later will not be a problem.
Any link or suspension arm is susceptible to corrosion in this country due to road salt, for instance I have just stripped a 350Z here that had SPL arms on, while still in working condition there is corrosion on them but hat doesn't make them poor quality.
If a set has genuinely snapped that has been supplied through Whiteline UK then I would be happy to talk to the customer and discuss it with the head of Whiteline UK Greame Jeram.