Overwintering a banana plant?

Sihitch. The problem is in getting them back into growth without them rotting. Its the same problem you get with many different types of tuber and rhizome, such as Colocasia, Amorphophallus, Gloriosa etc.

I am not that good at it myself. But I think the key is to have them in very very slightly damp compost, and then to not water them until you see green leaves appear. If a plant doesn't have any leaves it can't expire and make use of any water.