TEMPORARY TREASURES: FrostFrench, the London label designed and founded by Sadie Frost and Jemima French, is going the guerrilla retail route. Following the opening of the brand's first stand-alone store in London's Islington last month, the duo will open two pop-up shops in the city Nov. 10. One 300-square-foot boutique will be in Mayfair's Burlington Arcade, just off Piccadilly, while the other, a 500-square-foot space, will be on Fouberts Place, a row of trendy shops behind Carnaby Street. Sharon O'Connor, managing director of FrostFrench, said the pop-up shops would be open until at least February of next year, and added that the brand was also set to open a second permanent store in central London in March.