SOLE MATES: The merits and perils of high heels were a hot topic at shoe designer Nicholas Kirkwood's party Saturday night. Liberty Ross dispensed advice to ladies who live in fear of taking a tumble. "I wear my straps really tight so that the high heels feel like an extension of my leg," she said, hastening to add: "And I take cabs." Charlotte Dellal, the designer behind Charlotte Olympia, known for its the skyscraper high designs, said flats are not an option. "I have to wear high heels. Can you imagine not? They are all I design." The party was co-hosted by Browns in a grand Portman Square townhouse, with guests including Todd Lynn, Ben Grimes and Pauric Sweeney.