Well I think I have found the issue....
Humdinger your on the money with this one.
Today I loosened all the control arm bolts and re torqued them all up (at ride height). Also both panhard bolts to 170Nm. Did a rough check of the toe in and it must have been an optical illusion as it was near perfect.
So decided it was time to look at the tyres...first I took my unused spare and replaced one of the front wheels....... immediate improvement in the wobble, now if only I had another completely new unused tyre! I don't so decided to move the rear on the other side to the front, test drive and wobble is now only very slight.
I noticed the front tyre I took off had a distinct wobble across my flat garage floor:
https://clipchamp.com/watch/oam2gg5GSdV
So I checked the pressures of the tyres... they were all at 32psi which is way lower than I usually run them (38F 40R). When I had them balanced recently I remember the tyre shop mentioned something about the pressures being too high and they had let them down a bit... I didn't think much of it at the time... Luckily I have only done a few hundred k's with them at that pressure.
Now I have to figure out a way of getting all the tyres even running again, perhaps by increased rotation cycle maybe...