(Sorry, the smiley in the top line should be a :(
Glassons in New Zealand used (for some years) to do very light, bare-bones merino wool polo-necks in lots of different colours. They made fantastic, toasty base layers. Alas, they have stopped doing them. Does anybody know other companies doing similar?
(I bought a couple of M&S merino roll-neck sweaters but they are thicker, have a couple of fussy details and aren't really base layer type stuff.)