could be the bushes securing the rack, the are big round things that bolt the rack to the bulk head, i think the track rod comes with the rack and cant be bought seperatly (the nut on the end which rounds for a past time only comes with the rack!)
one way of finding out is to put it in for an MOT at a good garage, should be a failure,
when you are looking at this play make sure its not everything moving as a unit which is OK, this happens wheh the car is jacked up and movement can be seen on the top mounts on the shockers, this is because the car is off the ground and and the shockers are noit seated in the cups properly, nothing to worry about, make sure the nuts are tight.
if it were me i would always do the track rod ends and bottom ball joints first as a process of elmination, mine was fine till i got it off, they are cheap and easy to do compared with a rack,
there is nothing to wear ina rack really, play in the column means the wheels move together but not the same as the steering wheel, play elsewhere will mean the wheels move independant of each other
another essay, im going to bed