My LCR turned 3 years old last week so i had to get an MOT done and it failed on the drivers side ball joint!
For the past 6 months it always made a clunk when i drove onto my drive or over a speed hump but i just left it!
It was a bit of a pain in the arse to locate the part aswell. I twice got sent a normal seat leon ball joint. The LCR joint is bigger.
It didnt need a retest, as soon as it was fitted i got the MOT certificate.
However watch out if they replace it, i got my car back and the steering wheel was slightly off centre. If i straightened the wheel to the centre position the car would veer off to the right! I took it back, they made an adjustment and all is fine now, thank god!
Your car will be approaching 3 years old soon so i doubt they'll do it under warranty. Its wear and tear! It is a worn ball joint after all.
I do think this is a common fault after doing a few searches, a lot of people complain of front end knocking.