Bid4Spots, the Encino-based radio reverse auction marketplace, announced Tuesday that it has launched a new marketplace serving the United Kingdom. Bid4Spots said that the firm's UK site officially launches in Q3 of this year, and will hold weekly auctions on radio airtime. The firm's UK venture wil be headed by Paul Mitchard, a UK radio advertising veteran. Bid4Spots operates an Internet-based, reverse auction system for allowing advertisers to compete for unsold radio station advertising inventory.