Picked up a Sale Now On flyer as I came away from Screwfix today, and found this bargain. Black, all sizes at that price (edit: only M, L and XL left). Lifa Stay Dry technology. Deal button goes to L -- use link in comment 3 for other sizes. According to the flyer, the sale prices end on 8th January.
Helly Hansen Kastrup baselayer long sleeve crewneck Lifa 130gsm half price: £8.49 at Screwfix