Ah, the word 'damp' is the worrying thing. Pelargonium geraniums are able to survive temperatures as low as -10deg C, but what kills them is the combination of cold and wet/damp. They succumb to fungal infection rather easily during the cold, wet months, so where you really want to keep them is somewhere nice and dry. Like a spare room that's cool, if you have one. They're not going to be growing because you won't be watering them, so limited light isn't really an issue. I usually cut down the topgrowth to about 4-6 inches, removing any leaves which are browned or yellowed, and inspect periodically during the winter to remove any fallen leaves which are sitting on the compost. These are a source of fungal infection. When it gets to March, they should be potted up into fresh compost, pruned back a bit if they need it, watered and brought into full light and a bit of warmth, fed weekly, to get them ready to put out again at the end of May.