The ball is done now. It was straighforward after I cut the old one off.
I took time to check out the front caliper while everything was apart and it was the same as on my last GS. Partially seized. I gave that a good degrease, clean and regrease and the same for the other side and once again, the very slight wheel wobble has disappeared from about 75MPH upwards. It may have disappeared altogether if I went faster but 75 to 80 is just fine for me.