Yes you can. The corms become very congested causing some loss of vigour, especially in the centre of the clump. Lift and keep only the top most corms on the outside edge of the clump. These develop on top of each other and form chains.

Yiou can also divide them successfully in spring

I have just been out in the rain and lifted some from under the oak tree in my field. i am going to pot them up tomorrow. I think 4 to a 7inch pot should be alright.

I find crocosmia are not very happy in pots over winter Peter. Most will survive but they don't like their roots being very damp and frozen and you may lose them or they can be very slow to new growth in spring My advice would be to plant them outdoors and then if you want them in pots next year plant the up into the pots when the new shoots are 2 - 4 inches tall. I sell about 250 crocosmia a year and use this method successfully.