I would wait until the end of March when the soil warms up. If you plant any earlier then the bulbs will just sit and possibly rot. Prepare the soil and deep dig and you could also cover the soil with cloches to let the soil warm up.

I grow mine from seeds.

Thanks both of you so I will wait. I once tried them from seed but was not successful. I then read that it can be quite difficult to grow onions from seed but might try again.

The trick is to start the seeds indoors in little seed cups, usually in February. In April, when they reach a decent size, transfer them outdoors in rich loose compost with good drainage & full sun. You can always harvest the green onion tops which are delicious in soups and mashed potatoes.

Thanks, Bathgate. I will certainly give this a try indoors this time around.