How would you overwinter a large Ensete banana grown in a container rather than the ground?
Rot is the biggest issue for Ensete in winter. Big ones (5 feet of pseudostem or more) will be happy being stored dry - all leaves and roots cut off, upside down for a few days to drain, newspaper used to draw and water out - and then put somewhere frost free, but not warm (don't want to encourage it to try to grow!)
I plunge-pot mine in the garden in Summer, and bring the pots/plants in for the winter, but I have a tall conservatory. I give them a little heat, so 5C or below would be rare, and almost no water - after a wet autumn like this one the main problem is the pots coming in too wet - but if the plant has plenty of leaf that should help it dry the soil out.
If you store it dry, with the leaves chopped off, the next problem will be in spring - once re-potted and growing again the height of the leaf rollers is an issue with roof clearance, and the plant can't go out if there is threat of frost. If the pot/plant is not too big it could maybe go out for the day, and in for the night, in which case a garage or something frost free, but with enough ceiling height!, would do, but after 2 or 3 years the mother plant is going to be tall and heavy for that sort of in-and-out on a daily basis.