ME, JANE: It was like a family reunion for the Birkin clan Wednesday night at a cocktail to fete a collaboration between La Redoute, Jane Birkin and two of her offspring, Lou Doillon and Kate Barry. Doillon, in a sunflower yellow Alberta Ferretti dress, had to scoot off early to read love letters at the Theatre de la Madeleine. "We'll soon be taking the gig on tour around Europe and hopefully the United States," said Doillon, just back from Cannes, where she'd "enjoyed swimming at 6 a.m." and a whole load of movie stuff. "It's been a nonstop year for all of us," sighed Birkin, also just back from Cannes, where she'd premiered her first directing effort, "Boxes," loosely based on her family history.