Firstly thanks for all of the responses - swing axle Triumphs are a new thing for me.
The car in question is this one: https://www.gumtree.com.au/s-ad/kingsbury/cars-vans-utes/triumph-herald-coupe/1179188230
More on this in a moment.
Nick's comments about the use are pertinent: the car will not be staying a Herald in many respects. In 2015 I was gifted a fibreglass body which had been found sitting on a Triumph Herald chassis. The body looks like the pics attached - sorry for the poor quality, they are scans of when the car was found 15 years ago. The story is that the then owner wante to teach himself how to work on cars, so he bought this as a running and registered (taxed in UK terms) car and then proceeded to take it apart. He then found out that he actually had no mechanical aptitude and stopped and the car languished for 10 years in a shed. The owner prior to me found the car and 'saved' it from going to the tip. He was an Alfa enthusiast and did not like the Triumph chassis and running gear. He hoped to make a separate chassis and use Alfetta running gear and suspension on a home made chassis. However he did not realise the legal issues or the amount of work. More than 10 years passed, in which he sold off the chassis and papers to go under another Herald. The body then came to me along with a host of Alfa bits.
Now someone, somewhere put in a huge amount of work to make this and I think it's worth saving. The issue I face is that under Australian road rules if I make a new chassis, which I'm capable of, then the engineering fees to certify is will be over 5,000UKP. Plus the car would have to meet near current emissions - virtually impossible. So I plan to restore it to it's Triumph roots and argue the case that it is a re-bodied 'Herald'. The Herald I have found is a 1961 Coupe that is a basket-case, fred flintstone car - if you sat on a seat you'd go through the floor - but the chassis is mostly sound. I will give the body to some local Herald enthusiast in exhange for a bottle of red for a friend who will store the car. The front corners of the out-riggers are filled with dirt and rusty, but that is an easy repair. The main chassis rails, particularly around the diff are oily and sound. For me the best part is that the car has a Datsun A14 1400cc, 85bhp engine and 4speed gearbox. This is Nissan's copy of the A-series engine and they were very popular to transplant into Morris Minors etc in the 1970/80's and easy to get tuning parts for as well as happy revving to 6,500rpm.
So I have a chassis, a desired negined, and a car 'ID' that was registered in my state, plus a fibreglass body. Changes to the chassis will include replacing the sill structure with some RHS steel and welding a steel floor under the cabin section. Stiffening the chassis with some plates. Adding a roll hoop and proper seatbelt mounts - I don't like the holes through fibreglass. The a brake upgrade will have to occur, discs of some sort on the front. I have learn on this forum that the Australian cars were all Mk1 chassis, but with changes for export to make them tougher, which I'll have to investigate.
As for the use of the car, I want the car to be used for sporty sunday drives, motokhana's and perhaps the odd hillclimb. Ideally I want it to have as few vices as possible at the limit, even if that limits is at modest speeds. To make it easy to get back on the road then modifications to what is already present is the way to go. Rotoflex is expensive locally and hard to find and shipping of large parts from the UK to Australia expensive, hence the query about swing springs and camber compensators. The American forum is very pro compensators, but I'm concerned about loss of ground clearance as I plan to lower the car to have a little neg camber. So it seems that the swing spring is the go.
I hope this was not boring for all who read it, but I trust it fills in the gaps.
BTW all advice of handling and chassis issues are welcome