"...I'm personally not convinced that old houses are damper than new ones - new ones when all sealed up seem to suffer from far more mould and the like..."
Without question, it depends on the older house and the climate and location. An old stone cottage, maybe with a nice thatched roof in rural Devon would be less likely to suffer than an equivalent cottage in Aberdeenshire, if for no other reason than you'd be able to keep the doors and windows open for more months in the year.
Modern houses, simply because of all the insulation and well sealed windows are more prone to damp and mould, humans are messy wet creatures, put us in a sealed box and we will quickly contaminate it. The HUF design appeals because although it can be sealed up it is designed to be opened up to the outside world whenever possible.
"...Sorry but that HUF house just reminds me of a doll's house with the doors open and everything on display ..."
I get the dolls house reference and that is common, because people are looking at the house from the outside, if you stand inside one you see it differently, your garden, your wood are no longer something on the outside of your home, they are as much a part of your day to day life indoors as they are when you are out and about. However you do need to get used to not having furniture that is designed to rest against a wall (other than the shelves and such in the cellar).
Passive Solar Gain ( South Facing windows ) combined with intergral large Thermal Mass ( Stone wall / Fire ) would be the best option wouldn't it?
Oddly enough that is exactly what is happening at my Scottish home (my sisters place) we have wood burning stoves in each room, and have built a large glass extension down one side of the building turning the lower level windows into doors. The difference to the internal temperature of the house has been significant, just from the air warmed by the sun in the extension.
It is an old Perthshire farmhouse, the oldest part dates from the 1600s.
