My car (a 10 plate czech built i30) developed a knocking noise from the drivers side when going over speed bumps at about 10 mph so i took it into a Hyundai garage in Edinburgh. After having a look at it they said they found loose bolts on the front suspension thus causing the knocking noise (which i found hard to beleive). I drove the car home and it was still knocking so i thought i would try another dealership in Kircaldy.
The head mechanic took the car on a test drive and confirmed that both front suspension struts were needing replaced. He said that he had done a few Hyundai i30's with the same problem as mine and replacing the struts cured it. So i booked my car in and got both front struts done under warranty. Happy days no knocking 

[Lorian]

It's the plastic boots/bump stops on the top of them, their are two TSBs that relate to the problem. I have it too, it seems pretty common.

Did they do the back ones too? If not you might want to reach up over the wheels and see if the boots slide up and down of their own accord, they shouldn't  

Cheers but the back ones are ok