I had a similiar problem as you. Changed the UJs but didn't sort it. Checked the box for play but no luck. Swapped the track rod ends over as well as poly bushes on the front axle to see if it would fix the jerk/clunk but it would not go away. In the end it turned out that the bolts that held the aftermarket steering wheel to the boss were loose! :oops: :doh:
Having said that, you're probably not as stupid as me to miss that! Best of luck, mate. Hopefully somebody intelligent will come along soon! :D
Simon.