UK Stocks-Factors to watch on April 6

April 6 (Reuters) - Britain's FTSE 100 index is seen opening 38 points lower at 7,161 on Friday, according to financial bookmakers. * CONGO MINING: International mining companies have insisted that Democratic Republic of Congo amend portions of a new mining code to respect exemptions they were granted by its predecessor. * COPPER: Copper rose 1.4 percent on Thursday as fading concerns over the prospect of a trade war between China and the United States sparke