Heat Exchagers

OK I know there knowledge of geography may be iffy, but looks interesting.

So I looked more into Rotex, the US and Australian web sites have a lot more info.
If I have the numbers right we would need 2 or 3 for heating, with DHW 3 or 4. There is one type available that does not get a mention on the US site.

The tanks are ganged to meet demand
Heat is supplied from wood, solar or propane sources. You can certainly have solar as first, seems no reason why wood could not be second and propane third.
Issue maybe with heat, but water boils here at 192F, just under 90C