I had the same thing with my KA. First one side in one year, then the other side the next.
It cost about �175-�200 each time.
It is a common thing with KA's, bad news is that once it happens once, it means yor car is more susceptible to it, and it will reoccur. It was about 2 years between the first one and having to have the same side done again.
basically a rubber mounting at the top of each strut, 20 odd quid each from ford, common fault on the ka and fiesta im afraid, however they are SUPPOSED to have slight play but obviously not excessive. easy fix