barrie

I'm in the UK. My greenhouse temperature is set at 11c.
Your 6c sounds risky. Cavendish will certainly not survive, my larger specimens rarely last the 6 months at my low temps of 11c. Small pups tend to do better. In10 years of banana growing, I've still not yet managed to get a Cavendish to survive long enough to fruit.
That's my ambition before I die.
Basjoo will survive at 6c, but Orinoco and Rajapuri may well suffer.
Keep them as dry as possible, with minimum watering. You may notice the leaves one by one turning yellow, so a little water may keep them going but they really won't thrive at 6c. I often take a deteriorating plant into my house when I see the leaves yellowing, it's either that or lose them.
Good luck.

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barrieboy