In reply to stuart945: I have a Capilene 2, merino by Icebreaker, Berghaus Tech Tees with and without Zips and some calssic Helly Lifa stuff,
all good to a point... I find the Capilene very warm, so tend to only use it at this time of year (with a Helly if its really cold), rest of year I am a Berghaus man - cheap as chips usually from www.gooutdoors.co.uk, they have just done tech t shirts for a tenner in the last sale
the Helly stuff I usually run in or use as a "first" base layer when its proper cold.
Merino is great for travelling in and is dead comfortable when worn with jeans in the pub.
(in my humble opinion of couse!)
Colin