[Overboard]

Out of round tyres

Crook tyres are normally a shimmy problem rather than a death wobble problem. Same as wheel balance.

 

[Overboard]

I didn't have the "Death Wobbles" per se, but hhad a wobble in my steering since we purchased it. It was finally solved with something the dealers called a "Road Balance" which I suspect is an "On vehicle balance".

Different things. Road force balance is done on what looks like a normal balancing machine that has a large roller that pushes up against the tyre to simulate the pressure caused by the road.
Like this;https://www.youtube.com/watch?v=nbL9vMRbMCA

On vehicle balance is done with the wheel on the car and a roller moves the wheel up to speed but only exerts enough pressure to grip the tyre to make it spin and does it against the shoulder of the sidewall rather than against the tread.
Like this; https://www.youtube.com/watch?v=7UP97bO-MpU

 

[Overboard]

it looks to be the panhard rod bushes that fixed it

I would say these are the most common culprits.

 

[Overboard]

Now after all that time I had a wheel rotation and bang....head shakes going into violent shakes.

Surely that suggests that the problem is primarily wheel balance?

 

[Overboard]

So, while not on the voted list of fixes, rims are what ended up fixing my problems.

If new rims fixed it then there would have to be something wrong with the old ones which I expect should have been picked up while balancing.

 

[Overboard]

Start with your panhard bushes.