Simon
I think you will find its in the new ball joints, as you have replaced all 4 joints its still very tight and will probally take a few thousand klms to
loosen up.
new joints are very hard to moove when you try n rotate them straight out of the box where as your old worn ones could be rotated very very easy...
and now you have replaced all 4 of them movement is restricted once again like new.
Did you replace them yourselfs ?? you need a 10 ton press to make them moove in the trailing arms.
Have you have a proper wheel align and camber and castor adjust.
:thumb
I had the two left ones replaced a year or so ago, and I noticed the steering was 'a little stickier' for a couple of weeks. I was warned
about it, and it did go away.
Peter
You need to get your fron end realigned, that should fix your wandering problem