A firm opening by Wall Street gave UK shares an additional fillip over the lunchtime trading session.Miners are leading the advance, despite conflicting views in the broking community on their merits. Societe Generale is in the bearish camp, cutting sector giants BHP Billiton and Rio Tinto from 'buy' to 'hold' and Chilean copper miner Antofagasta from 'hold' to 'sell'.Goldman Sachs, however, is riding the bull, and issued a research note forecasting a surge in global demand for commodities, which will drive the share prices of mining stocks higher.The big gainer of the day, however, is bus and rail group Arriva, which has revealed that it has had an unsolicited bid approach. Earlier this month Arriva said that talks with France's state railway group SNCF about a merger between its transport business Keolis and Arriva had ended. The failure of those talks stoked takeover speculation and shares in the company climbed yesterday amid rumours of a possible 700p-a-share bid from German transport operator Deutsche Bahn. Singaporean firm ComfortDelGro, the operator of the London bus company Metroline, has also been mentioned as a possible bidder. The shares have motored forward to a 52-week high, and have picked up sector peers FirstGroup, Stagecoach and National Express along the way. After being under the cosh yesterday following disappointing results security services group G4S is receiving another battering today as rumours circulate that a massive placing of the company's shares is underway in the City. Around 141m shares have reportedly been placed by RBS at 250p per share. The shares represent around 10% of the issued share capital of G4S and were held by major shareholder Skagen Trust, which acts for the family of company founder Jorgen Philip-Sorensen. Hedge fund manager Man Group is another poor performer after its flagship AHL fund lost value last week. Broker Morgan Stanley has cut its price target for the stock from 340p to 260p.Marks & Sparks is in the doldrums after as JP Morgan cut the stock's rating to 'underweight' from 'neutral', but elsewhere in retail broker comment has given a lift to B&Q owner Kingfisher. HSBC has upped its rating from 'neutral' to 'overweight' and reckons the company's 'underused balance sheet offers potential for international expansion and/or sector consolidation.' Brokers were queuing up yesterday to suggest that full-year results from generic drugs maker Hikma Pharmaceuticals would be ahead of market consensus, which may explain the negative response to the 33% increase in 2009 operating profit it announced this morning. Military decoy specialist Chemring radioed in a 5% increase in trade during the four months to the end of February at constant currency despite taking a hit from snow storms in both the UK and US.Black cab maker Manganese Bronze is to cease production of bodies and chassis at its Coventry plant with the loss of 60 jobs after more heavy losses in 2009 and further losses forecast this year. The group is also considering a further fund raising to fund vehicle assembly less than a year after it raised £9.4m. Chinese partner Geely is underwriting the placing and will take a controlling stake.Mainland European newspaper publisher Mecom continued to feel the pinch of the global economic crisis last year as advertising revenues slumped. Vehicle hire group Northgate reported an improvement in utilisation rates of its fleets in the four months to 28 February in the UK and Spain. In the UK, it achieved an average utilisation rate of 91% during the period, a 5% improvement on the rate achieved for the same period the previous year.Gaming software specialist Playtech's underlying profits rose by a quarter last year as it got a boost from its joint venture with bookmaker William Hill. Australia's Seeing Machines has won its biggest deal with the mining industry so far after selling its Driver State Sensor (DSS) computer vision product suite to BHP Billiton. The mining giant's Navajo Coal Company and San Juan Coal Company units will fit their entire haul truck fleet and a number of ancillary vehicles with the group's technology.Derwent London, which rents out offices in the capital, remained stuck in the red during 2009, but a "substantial recovery" in central London property values during the second half of the year has continued into 2010.Online banking systems group Neovia's total revenues declined from $75.9m in 2008 to $64.5m in 2009 with the loss after tax for 2009 $9.8m (2008: $8.1m). "The fourth quarter of 2009 saw stronger performance for both the e-wallet and NETBANX businesses compared to the third quarter, and revenue for the first two months of 2010 was in line with management's expectations," it added.Shares in oil and gas firm Aminex jumped after it announced that identified several potential oil and gas bearing intervals in its Olympia Minerals-1 well at Shoats Creek, Louisiana (OM-1).Baltic Oil Terminals is wanted after the company, which operates terminals at the Russian port of Baltysk in the Kaliningrad territory, said it had settled a dispute with former director Vladimir Gavrilov, reducing the company's liabilities by $1.4m.Ass one legal dispute ends, another begins, with Hochschild Mining taking Canada's Minera Andes to court in New York over a $65m loan provided for their joint venture San Jose gold and silver project in Argentina.