Three superstar designers have upped the style quotient at a trio of just-opened bars in Europe. • In Paris, Terence Conran has transformed the cavernous space once occupied by the Whiskey-A-Go-Go into happening Wagg (62 Rue Mazarine; 33-1/55-42-22-00). • Paintings of nudes hang on the walls of Milan's Mia Divina (Via Molino delle Armi and Via della Chiusa; 39-02/5843-1823), a kitschy-but-cool discotheque by Fabio Novembre, who has done stores for Blumarine. • And for London's long-awaited Sketch (9 Conduit St.; 44-870/777-4488), owner Mourad Mazouz of the red-hot restaurant Momo brought on Australian furniture guru Marc Newsom.