Crocosmia

Yes, they will grow. Most crocosmia are tough as old boots. The more common orange variety is more invasive than some of the other ones.

You can dig up the whole plant (you're unlikely to find all the corms if it has been there for years) and then just replant some of the corms. They normally grow as a string of corms and I am inclined to just replant the top two of each group. The further down the string of corms you go the less viable they are.

Just cut off the ones you want to use and, if it's a very invasive variety, give the rest to someone you don't like :D. A sharp knife will cut through beteen the corms. Some people just snap them off.

The very deep red varieties like 'Lucifer' are a bit more difficult to propagate and are less invasive.