LONDON, May 30 (Reuters) - U.S.-based power producer Calpine Corp. (CPN.N: Quote, Profile, Research) has sold a British power station to the UK's International Power Plc (IPR.L: Quote, Profile, Research) and Japan's Mitsui & Co. Ltd (8031.T: Quote, Profile, Research) for 500 million pounds ($912 million), the Financial Times newspaper reported on Monday.International Power will take 70 percent of the Saltend unit under a partnership which will hand the other 30 percent to the Japanese trading house, the FT's Web site (http://www.ft.com) reported without citing sources. No one from International Power could be reached for comment. A Mitsui spokesman said...