British shares flat; Fevertree, Intu underperform

(Reuters) - UK shares were largely unchanged on Monday, with trading volumes thin due to a U.S. holiday, while premium tonic water maker Fevertree and mall operator Intu Properties tumbled among smaller stocks.The FTSE 100 and the FTSE 250 were flat by 0806 GMT. However, oil heavyweights Shell and BP advanced as crude prices hit their highest in more than a week after two Libyan production bases began shutting down amid a military blockade. [O/R]With many investors away due to U.S. markets..