Rouge if you drop some pipes down and add a couple of radiators you might find that is all you need to clear any damp up? Going for the lime wash look over the natural surface will give a nice cottage feel down there and look rather good. Still treat the walls for fungal first with stiff brush. Assuming you have neighbors then the only real problem walls will be the front and back ones. Once it is all in use i don't think you would ever notice it again.