UK Stocks-Factors to watch on April 6

April 6 (Reuters) - Britain's FTSE 100 index is seen opening down 67 points at 7,264 on Thursday, according to financial bookmakers. * SHELL: Royal Dutch Shell sold its stake in a New Zealand gas field while taking over the field's operating company as part of a plan to possibly divest its holdings in the country later on, the company said Thursday. * TESCO: UK retailer Tesco Plc is cutting night shifts for shelf stackers in some of its supermarkets in a fresh shakeup that put