I just let the seeds fall or scatter them where I want them to grow. They sprout in early spring. Winter cold will take care of them. You are in the UK though, with different climate.

To store them, just let them sit out on a paper plate for a few days to dry, then seal them in a plastic baggie or a paper envelope and keep in a cool place in a glass jar till late winter and then scatter them outside. They do not transplant well. No need for the wet towel.

Thank you for the advice! I shall give it a try.

karen - I'd be inclined to sow them thinly, immediately in pots, protect the pots from mice, birds heavy rain, etc. and leave them out all winter. Plant out the entire pot to avoid transplant issues. If you have a cold frame I'd use that. I believe that sowing the seed fresh now will be more successful than saving and sowing later. If you have a lot of seed you could also try sprinkling a few in situ. I can't grow them where I am but I had this advice from a chap who runs a large garden open to the public in Devon.

You are so lucky to have the soil for the blue Meconopsis!

Here is a link that might be useful: Meconopsis