Aug 9 Britain's FTSE 100 index is seen opening up 9 to 11 points higher on Tuesday, or up as much as 0.16 percent, according to financial spreadbetters, with futures marginally up ahead of the cash market open. * The UK blue chip index closed 15.6 points higher on Monday at 6809.13 points to touch its highest level in more than 13 months on the back of gains in mining stocks and Barclays, which was boosted by an upgrade.