There is nothing that can make you feel warm and cosy like a much-loved sweater. Worn over jeans or leggings, this can be a great casual look. Add a pencil skirt and heels, and a sweater becomes something completely different.  It is an integral part of any respectable capsule wardrobe, and of course, in recent years it has also become an undisputed star of the Christmas season. Everyone who is anyone has to have at least one Christmas jumper. Selfridges would not necessarily be your first port of call when looking for a perfect jumper, but this season, they have pulled out all the stops to offer you the most…