UP TO THE MINUTE: Don’t be fooled by Sienna Miller’s polished fashion sense. “I’m terrible. I don’t have a stylist. I leave getting ready right to the last minute, and then run around and throw something on,” she said with a laugh at the party following her Twenty8Twelve show Sunday night. Miller was fresh off a flight from Los Angeles where she’d been attending pre-Oscar parties, and had only one thing on her mind for the rest of the week. “Sleep!” she said. Revelers at Mayfair’s very cool Whisky Mist club included Miller’s sister Savannah, who co-designs the collection, Roisin Murphy, Rachel Hurd Wood and Matthew Williamson.