YANKEES INVADE LONDON: Jeff Koons and Beth Ditto held court in different corners of London Wednesday night, showing their British pals just what American creativity is all about. Koons held a private view of his show “Popeye Series,” which runs until Sept. 13 at the Serpentine Gallery in Hyde Park, with guests including Stella McCartney, Alasdhair Willis, Mike Figgis and Tracey Emin. Meanwhile, over at Sketch, the restaurant and club near Oxford Circus, curvy crooner Ditto showed off her new collection for Evans, the plus-size brand owned by Sir Philip Green’s Arcadia Group. Guests included Green, Kate Moss, Simon Cowell, Pam Hogg and Yasmin Le Bon — who will be doing a line for Wallis, another of Arcadia’s brands, in September. “I wanted to make something special, just for us, something never seen before,” said Ditto. “I hope the clothes inspire you to think outside the box.”