I don't think you are still asking this question after the recent cold weather... The fact is, in their natural environment Fuschias do not go completely dormant. That is because temperatures in S America are never below freezing. It follows therefore if you keep them above freezing they will keep their leaves. Nevertheless at low temperatures their growth becomes extremely slow, so it is wise to keep them dry during this period. Light is not a critical factor in winter for Fuschias.