Brett, what's wool 1? I thought Patagonia's lightest wool layer was called wool 2.
Mark, I think a simple wool or synthetic base layer is all that's needed for sleeping. I usually use the shirt I'm wearing througout the day for my upper body, plus perhaps another layer, and bring Underarmour base 1.0 bottoms or Smartwool midweight tights for my legs. The few times I used that Skaha Plus I sold you, I discovered how great it is to wear an insulated jacket as a sleeping layer, so maybe give that a try too on trips that are cold enough, even in a mummy bag I found some definite comfort advantages to wearing a jacket at night. Also, like Brett said, UL is multiuse. I generally wear my sleeping layer on my legs, then wear my Goretex rain pants over that. I don't think it's so much of a vapor barrier, like some say, as it is, just a wind barrier--it stops heat loss from my legs through convection.
I haven't used the new UL merino clothing that BPL sells, but that looks like the ideal sleeping layer--wool and very light. A problem I sometimes have on very cold nights is that I'll be too warm when I go to bed, overheat after I fall asleep and sweat, then wake up later because my synthetic clothing is flash freezing me. Wool regulates moisture much more comfortably than synthetics so I try to bring as much as I can, but on trips where I only use a base layer for sleeping, the wool shirts I have can be a heavy option.