They need to be placed in a frost free place. A garage is good as it is quite damp. The key is keeping damp enough to see them through to spring without causing them to rot. A spray of water every fortnight would be good.

Label them whilst you can still see the flower colours! When the frost has blackened the tops, dig them up carefully so as not to damage the tubers. Shake off as much soil as you can and trim the tops down to about 6 inches. Put them in a tray upside down for the first month or so to let any moisture drain from the stems. You can lightly cover them with dry compost but don't use plastic to cover them. Keep them in a frost free place. They don't need light til Spring. Sprinkle a few slug pellets among them to kill off any that are hiding.