Just an update for anyone that's interested.
I have had the battery, dual input DC to DC charger, and the new AC charger installed by a qualified auto electrician, and am very pleased with the results. Although I could have done the installation myself, there is no way I would have done as neat and tidy job, and he came to my house and did it. I charged the battery and did a capacity test by switching on everything I could in the van, which drew around 17amps max, and let it run until the fridge would no longer operate. The end result was a capacity of 204 amp hours. So I'm very happy with that. The power tech AC charger put out the full 30amps as advertised, and the power tech dual input charger was putting in 10.5 amps from my 200w portable solar panels, and was working well when charging from my car, although the battery was nearly full when I tested that side of theDC to DC charger. All in all, a nice neat package. All up price including installation was approx $2,500. Considering a good quality 200ah AGM was going to cost upwards of $700, giving me only half the useable capacity for 3 times the weight, and 1/3 the life, I was happy to go the down the lithium path.
Cheers
Dave