When the cold takes all the foliage off the plant you might find everything dies back to a tuber or two close to where the roots were...
Otherwise you are into lifting the whole plant before the frosts, trimming off the bulk of the foliage and roots and trying to nurse it in a bucket of water indoors.
That is not so bad if you have a well lit window or strip light you can put over them, if you set it to grow semi dormant in a 6" pot of clay/loam, you may find an indoor grown plant limps along making quite a few tubers through Winter.
You might find a cold frame over a small dug in tub of water is just enough to keep tropical waterlilies ticking over through Winter as far South as you are, with good sun on a frame you may find that is just enough to keep the tubers ticking over all Winter
Regards, andy
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