Encino, Calif. - Bid4Spots, an online marketplace that features reverse auctions for radio advertising time, announced on Tuesday that it plans to launch a version of its service for the U.K. radio market. Encino, Calif.-based Bid4Spots' U.S. marketplace is used by more than 2,300 radio stations, 1,300 advertisers and 260 ad agencies. Set to debut in the third quarter of 2007, the company's U.K. site will be run by AuctionMedia.