By Sara Sjolin, MarketWatch

LONDON (MarketWatch) -- Shares of Pearson PLC and Aggreko PLC led U.K. stocks lower on Friday, trimming the benchmark index's monthly gain to 4.5%.

The FTSE 100 index edged down 0.1% to 6,800.51, partly erasing a 0.2% gain from Thursday.

Posting the biggest loss in the index, shares of Pearson slumped 6.6% after the publisher of the Financial Times said full-year operating profit declined due to weakness in its U.S. education business.

Aggreko gave up 3.6% after the temporary-power company said Chief Executive Rupert Soames will leave the firm to become CEO at Serco Group PLC . Shares of Serco Group rallied 6.8%.

As a sector, mining firms added to the pressure, as they tracking most metals prices lower. Shares of Randgold Resources Ltd. dropped 1.5%, Antofagasta PLC lost 1.3%, Rio Tinto PLC (RIO) erased 1.1% and BHP Billiton PLC (BHP) slipped 0.4%.

Sentiment was also hurt by a negative mood in the rest of Europe after better-than-expected euro-zone inflation data eased pressure on the European Central Bank to act at its meeting next week. Economists have recently worried that the region was heading toward deflation, increasing speculation that the ECB would either cut rates or use unconventional easing measures to loosen policy at its March meeting.

Banks moved lower, with shares of Standard Chartered PLC down 2.1%, Royal Bank of Scotland Group PLC (RBS) off 1.8% and HSBC Holdings PLC (HSBC) 0.9% lower.

On a more upbeat note, shares of Old Mutual PLC climbed 5.1% after the investment firm lifted its full-year dividend and said adjusted operating pretax profit rose last year on a constant-currency basis.

William Hill PLC gained 3.9% after reporting an increase in full-year profit as it benefited from a strong revenue at its online business.

Mondi PLC advanced 4.1% after the paper and packaging firm reported a 22% rise in headline underlying operating profit for 2013.

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