By John S. McClenahen The Conference Board's leading economic index for the UK rose a tenth of a percentage point to 134.0 (1990=100) in August, the most recent month for which data are available. The index was unchanged in both June and July, says the New York-based business research group. But across the English Channel the report was even better. The Conference Board's leading index for France was up three-tenths of a percentage point to 105.3 (1990=100) in August, its sixth consecutive monthly increase. "There were upward revisions to several previous months, and the strength continues to be widespread," says the Conference Board. "As a result, the growth rate of the leading index has remained relatively steady in recent months at about a 4% annual rate."