Trailing Begonia

These have been magnificent this year and it seems a pity to relegate them to the compost heap. At what point do I lift the tubers and where do I store them and how do I store them please?

 

that's what I do: I wait for the very first frost to come (shouldn't harm the plant because its in the pot and the soil will make sure it doesn't freeze - although, I have plenty of soil in the pot:-)
then I get the tubers out and store them in some dry soil which I moisten now and again over the winter. Storage as cool as possible , but I don't have anything lower than 10 to 15 degrees at my house and that has been ok ( for a few years now)