UK Stocks-Factors to watch on May 9

May 9 (Reuters) - Britain's FTSE 100 index is seen opening 1 point higher on Tuesday, according to financial bookmakers. * GLENCORE: Glencore said on Tuesday it has begun a sale process for its Tahmoor coking coal mine ahead of plans to halt operations next year, adding to a growing number of collieries on the block in Australia. * DIAGEO: Diageo, the world's largest spirits company, stood by its medium-term sales and profit targets on Monday, saying the year has progressed wel