Had a bounce up and down and got out of the passenger side and lo and behold a 5 mm gap on the passenger side rebound spring. The drivers side had closed up to maybe 2 mm.
So maybe more bouncing and waggling would settle both sides, but there was me thinking there was something wrong with the springs. You learn something new every day so still a very useful exercise for me Bob!
I'd like to upgrade to Rutherford springs but at 13,000 miles I was waiting until the kingpins needed looking at.