I would think woolies should be on the tighter side; too loose and they might not fit under other stuff.
What size I wear depends totally on the brand! Size creep is a wonderful thing. Seriously, I am a true extra small in Ibex tops, but a small on the bottom. However, there some Ibex styles in pants that I just can't wear. The x smalls are way too tight and the smalls are too big. I don't have any woolies, so I can't be specific, but you may well wear an x small.
My red half zip Shak came already! I know you didn't like the feel of it, but it is good for hiking as either an mid layer or top layer. I wore my black one once for cycling in the cold and it was too warm! I also ordered 2 micro weight smart wool tops, but I have to try those on...