I'm looking at adding pumic, or perlite to produce an insulting concrete.

Yes I've looked at the Hockerton project before, one of the better efforts in my view.

Yes the moisture issue is one that is found in underground homes, as such I would want to include an air conditioning system with de/humidifer. (Which would avoid the need for underfloor heating, as I hear from so many people about it leaking!)

I really want to avoid foam on the basis that can burn and produce noxious fumes if there is a fire, could compress over time, and deterate either by aging or pest attack.

Plus I want to use the outer concrete layer not just for insulation, but also to double as a waterproof layer, thus not requiring any further layers of waterproofing material to be added. (As long as that fits with planning regulations..)