I saw Never Let Me Go a few nights ago and the wardrobe is incredible. Keira definitely has the smaller part, but it some ways it's more compelling. Lots of layers; many very comfy-looking sweaters, wellies, and jackets, since it takes place in the countryside. Color scheme was mostly beige, olive green, brown, and black, with a little navy blue.
My favorite outfit on Keira was a knee-length green jacket cinched at the waist by a light brown belt over a black dress and wellies. It fit her frame beautifully.