In reply to Paul Atkinson:
An R1 hoody would be fine. I never put anything more than that under my jacket, but I reckon something like a nano puff would probably fit. I use arcteryx phase AR baselayers for winter. I prefer to overlayer with synthetics. I tried a size small but it was too restrictive. I do like close fitting clothing.
They sell them in the square shop part of outside.
Col.