Donkey jackets (if you can find one!) are they the ultimate heavyweight wool shirts? They're like them spendy made in NZ (via China) shirts only more wind resistant and a fair bit cheaper. Discuss.
A good peacoat will keep you snuggy warm. The double breasted front keeps the wind out better than a donkey jacket.
Could you not use a thermal t-shirt and Norgie top to the same effect?
In reality a cheap fleece is as warm as a wool shirt but not really bush uniform.