As has been said, it depends on what the remainder of the winter has instore, for as well as the previously mentioned die-back, pruning now could induce the production of new shoots which could be damaged by further periods of very cold weather. Already here in Cornwall, due to the very mild conditions we have had since the new year, things are beginning to 'creak' into action (roses, Hydrangeas, camellias etc) but the last few very cold nights will slow that down again. We still have a long way to go with this winter so, I agree hang on until end of Feb or even mid-March.
Lannerman