London has opened sharply lower, with sentiment not helped by a mild profit warning from Rolls-Royce and a bad-tempered G20 meeting.Aero-engine maker Rolls-Royce is one of the few risers in fact, despite warning solving the problems on its Trent 900 engine will mean it making less money than expected in 2010. Miners, though, are big fallers this morning on disappointment with the outcome at the G20 meeting and the possibility of a currency free-for-all. Xstrata, Antofagasta, ENRC and Anglo American are all under pressure. Down a division, Electrocomponents is storming ahead after the world's largest distributor of electronics and maintenance products, forecast full year profits will be ahead of previous expectations after a strong first half. All regions saw double-digit percentage underlying sales growth in in the six months to 30 September. Year on year revenue growth quickened in the third quarter at media agency Aegis. Total group revenues in the third quarter were 8.8% higher than in the corresponding quarter of 2009. Revenues in the first nine months of 2010 were 4.4% higher than a year earlier.Less volatile markets have trimmed activity at money broker Tullett Prebon, with business 'relatively subdued' over the past four months. Revenue in the four months July to October of £292m was 3% lower than this time last year (6% lower at constant exchange rates).Oilfield services firm Petrofac has won a three year contract from Maersk Oil. The contract, worth more than £40m, is for the provision of engineering services to the UK Continental Shelf assets of Maersk.Instrumentation and controls company Spectris has seen a revenue growth spurt in the second half of the year, prompting the group to raise profits guidance. Revenues for the four months ended 31 October 2010 increased by 21% from a year earlier, including a contribution from acquisitions of 2% and beneficial effects from currency of 3%. Housebuilder and contractor Kier's construction businesses are offsetting a slow start to its homes arm as the housing market struggles, while Hornby is making "encouraging progress" and the toy company that owns the Corgi and Airfix brands says its new Scalextric range is selling like hot cakes in the run up to Christmas.