I feel a bit of a philistine after reading all the sensible ways to look after geraniums through the winter. All I do is pull them out of the ground and chuck them straight into a black bin liner. I usually stash about 40 plants in three full bin liners. I then just leave then somewhere, shed, under trees or wherever they drop. If outside they may get an old blanket thrown over them. I actually buried them all (not in bin liners) one year after reading an old gardening book. In the bin liners they go mouldy, the tops rot off and you think you've really done it this time. Just cut them back in the spring. I lump them all in a few big trays, usually in the greenhouse or frame, to keep an eye on them. 99% and all of the buried ones survive and shoot out. Every year I think that I ought to do it properly but never seem to get round to it...