Hi Paul
Here are some of my thoughts based on some personal experience:
Polypropylene – felt rough, a little itchy, prone to static electricity build up and seemed to hang on to body odours even when washed, thin layer so not too bulky.
A modern wool blend – felt warm, no itches (surprised me!), felt nice against the skin, required special washing machine program, got decimated by moths, expensive, thin layer so not too bulky. No static.
Capilene (proprietary artificial material from Patagonia) – draped well, didn’t feel rough, stretchy, warm, wicks moisture away from body to outer surface of garment, expensive, thin layer so not too bulky. Less likely to produce static.
Polar fleece (a Helly Hansen bib-and-brace) – felt warm, no roughness, stays dry, a bit expensive, slightly bulky. Some static.
Some of the above gear goes back several years, so material technology may have improved thus rendering some of my findings obsolete.
My personal preference for cold astro camps where it will drop below 4 deg C is a freezer suit I purchased from GTB Owl (see Kev’s post). Mine is slightly over size as I don’t like restrictive clothing.
My personal preference for around 7 or 8 deg C is woollen thermals with ski pants and ski jacket.
When I first arrived from the UK I didn’t really feel the cold but after some 16 years, I’ve turned into a softie or my blood has thinned!
Cheers
Dennis