Judder, Potentially Bad Control Arm

I have a slight judder/vibration on an Audi S4 which is felt through the car (not the wheel). It is felt normally at higher speeds (70mph) and is not always present. When I originally bought the car (used) a mechanic who inspected noted that there was some play in the offside control arm (unfortuanatly he didn’t state which one, of which there are 4). I’ve since had the car checked by two other mechanics – one couldn’t find any play, but one could in the offside lower rear arm.

The mechanic who found no play said this could be due to weather conditions (wet and dry for example). He did do a road test and could hear a very slight noise on the offside which he said shouldn’t be there (I cannot hear it), and advised me to wait until my next service to see if it has worsened and to look again.

I find the vibration annoying so would like to get it fixed sooner than this, however the fact that the above mechanic couldn’t find any play concerns me.

My wheels have been balanced several times, every time I get them balanced the next mechanic to do the balancing says they were previously out of balance, which seems quite odd to me. I’ve not had them aligned.

I’m due to have my tyres replaced soon, so this is perhaps a good troubleshooting step which will occur “naturally”, and allows me to eliminate one source of the problem.

Is there any other way I could be more certain about the cause of the problem?