UK Stocks-Factors to watch on May 23

May 23 (Reuters) - Britain's FTSE 100 index is seen opening up 9 points at 7505 on Tuesday, according to financial bookmakers. * At least 19 people were killed and 59 wounded in an explosion at the end of a concert by U.S. singer Ariana Grande in the English city of Manchester on Monday, in what two U.S. officials said was a suspected suicide bombing. * ROYAL BANK OF SCOTLAND: Royal Bank of Scotland is close to settling a costly and potentially embarrassing case alleging it