I searched and found
"dig up and divide monster clumps either in late autumn or in spring when the plants have just started back into growth. Each crown should be detached with its own roots, and although it can be directly replanted, it will get going more reliably when potted up and allowed to establish."

http://www.telegraph.co.uk/gardening/3335675/How-to-grow-Cirsium-rivulare-Atropurpureum.html

If you've left the seedheads on, cut them off and put them in a paper bag. Store in a cool dry place until the spring, when you can sow the seeds in trays or pots, covered with vermiculite. They need some heat to germinate, (18 degrees) which takes 7 - 14 days.