UPDATE 1-FTSE 100 dips as miners, exporters drag, Metro Bank tanks

A fall in blue-chip copper miners and a firmer sterling kept the FTSE 100 lower on Thursday but strong results from Shell and Smith & Nephew capped losses, while mid-cap Metro Bank tanked after an accounting error caused quarterly profit to halve.

The FTSE 100 was held to a one-month low as it fell 0.1 percent and the FTSE 250 was 0.5 percent lower by 0811 GMT, ahead of the Bank of England's expected rate decision. Sterling gained after investors took comments made by Prime Minister Theresa May as an indication of progress in Brexit talks between the government and the main opposition Labour Party.

A stronger pound hurts the blue-chip index, which books more than 70 percent of its earnings overseas. The currency could rise further if one or more BoE Monetary Policy Committee members vote in favour of hiking interest rates later on Thursday. "While there is speculation that the meeting might have a hawkish tilt, it is hard to imagine how the MPC can be anything other than neutral," CMC Markets analyst Michael Hewson said.

The BoE meeting follows the U.S. Federal Reserve's decision to hold interest rates steady on Wednesday. Shares of dollar earners such as British American Tobacco and Diageo shed nearly 1 percent.

Copper prices hit a more than two-month low, causing an index of miners to fall for the seventh consecutive session and leading heavyweights Rio Tinto, Glencore and BHP about 1.5 percent lower. But Shell, the biggest FTSE 100 company by market value, rose nearly 2 percent after beating quarterly profit expectations.

Medical products maker Smith & Nephew also outperformed the main bourse with a 3.6 percent gain, as it forecast annual revenue growth at the top half of its prior guidance range. On the mid-cap index, Metro Bank slumped 10 percent to an all-time low after saying the fallout from an accounting error it disclosed in January hit quarterly profit, capital buffers and major business customer deposits.

Among smaller stocks, plus-sized fashion retailer N Brown surged 13.2 percent as its annual core earnings rose, while cleaning products maker McBride sank 10.5 percent after its second profit warning this year.