July 3 (Reuters) - Britain's FTSE 100 index is seen opening 17 points higher at 7,565 on Tuesday, according to financial bookmakers. * RIO TINTO: Rio Tinto wants copper, and it's ready to pay top-dollar. The global miner would be willing to fork out a large premium over market value to secure a prime asset as it tries to reduce its reliance on iron ore, company and banking sources told Reuters. * ASOS: Online fashion retailer Asos is set to name Adam Crozier as its next cha