- Miners fall as BHP warns of slowing steel production in China- OBR to raise UK GDP forecasts for 2012- ARM, National Grid, United Utilities rise after upgradesThe FTSE 100 slumped in the opening hour on Tuesday as the miners dragged the blue chip index into the red for a second day.According to the Financial Times, the Office for Budget Responsibility is to revise its UK growth forecasts higher in tomorrow's Budget. Economist expect the OBR to up its GDP growth estimate from 0.7% to 0.8% for 2012.In other news, China has raised its fuel prices for the second time in less than six weeks. The world's second-largest oil consumer upped prices by 600 yuan ($95) a metric ton.MINERS DROP ON FLATTENING STEEL GROWTHMiners were the laggards of the morning after BHP Billiton warned of slowing steel production in China. "The big infrastructure build clearly will come to some end," BHP's iron ore President Ian Ashby told reporters in Perth. "Steel growth rates will flatten, and they have flattened, and we still see positive growth out to the middle of the next decade." BHP Billiton, Rio Tinto, Randgold, Vedanta, Kazakhmys, Antofagasta, Fresnillo, ENRC and Anglo American dominated the fallers list early on.Shares of Royal Bank of Scotland fell on reports that it is to close its equity capital market and corporate finance units in South Korea, alongside its cash equities businesses in Indonesia, Korea and Singapore. A total of 70 persons will be affected by the moves. Sector peers HSBC, Barclays and Lloyds were also out of favour early on.Chip designer ARM Holdings was a high riser of the morning after Barclays Capital raised its rating from equal weight to overweight and Investec upgraded the stock from hold to buy. Utilities peers National Grid and United Utilities were also being helped higher by upgrades from HSBC and Nomura, respectively.Concerns about Anglo-Swedish drugs giant AstraZeneca's pipeline are likely to increase as the company abandoned work on its anti-depressant treatment TC-5214, which it developed in conjunction with US peer Targacept. Shares edged lower.Advertising and media giant WPP fell after announcing its 10th acquisition for the year, buying a minority stake in Pakistan-based marketing agency Coverge Technologies for an undisclosed sum.FTSE 250: REGUS TANKS DESPITE STRONG PROFITSOffice space provider Regus fell over 6% despite reporting operating profits that more than doubled in 2011. The firm said profits came in at £50.6m, up from £23.9m in 2010, with sales up 12% to £1.16bn, in line with analysts expectations. The company said it would open 200 new offices this year.SuperGroup, the fast-growing owner of the Superdry brand, rose after revealing that it is to change its finance director and create a new role of chief operating officer.Retailing peer Debenhams was in demand after saying that like-for-like sales in the first half of its financial year edged higher, with growth accelerating towards the end of the period.Oil firm Cairn Energy advanced after it racked up a $1.19bn loss in 2011 but said it was still optimistic about striking it big in Greenland. BCFTSE 100 - RisersVodafone Group (VOD) 169.75p +1.43%National Grid (NG.) 640.00p +1.27%ARM Holdings (ARM) 587.00p +1.21%Whitbread (WTB) 1,740.00p +1.10%Tesco (TSCO) 334.45p +1.04%Legal & General Group (LGEN) 135.80p +0.74%Sainsbury (J) (SBRY) 306.70p +0.69%United Utilities Group (UU.) 610.00p +0.58%Hargreaves Lansdown (HL.) 493.80p +0.55%Capita (CPI) 750.50p +0.54%FTSE 100 - FallersFresnillo (FRES) 1,723.00p -2.98%Rio Tinto (RIO) 3,513.00p -2.81%GKN (GKN) 210.00p -2.51%Kazakhmys (KAZ) 941.00p -2.49%Antofagasta (ANTO) 1,217.00p -2.33%Randgold Resources Ltd. (RRS) 6,410.00p -2.29%Evraz (EVR) 396.10p -2.05%Vedanta Resources (VED) 1,389.00p -2.05%BHP Billiton (BLT) 2,006.00p -2.05%Eurasian Natural Resources Corp. (ENRC) 675.00p -1.82%FTSE 250 - RisersCable & Wireless Worldwide (CW.) 37.11p +6.36%St James's Place (STJ) 384.10p +3.17%Henderson Group (HGG) 130.50p +2.27%Babcock International Group (BAB) 760.00p +2.22%Cairn Energy (CNE) 338.00p +1.84%Debenhams (DEB) 77.00p +1.72%Ocado Group (OCDO) 129.40p +1.09%Micro Focus International (MCRO) 466.90p +1.02%Jupiter Fund Management (JUP) 241.00p +0.84%Domino's Pizza UK & IRL (DOM) 455.50p +0.77%FTSE 250 - FallersRegus (RGU) 106.40p -5.67%Exillon Energy (EXI) 195.30p -4.73%Ferrexpo (FXPO) 326.90p -3.14%AZ Electronic Materials SA (DI) (AZEM) 288.60p -2.99%Aquarius Platinum Ltd. (AQP) 156.30p -2.50%Bumi (BUMI) 756.00p -2.45%BlackRock World Mining Trust (BRWM) 685.50p -2.35%Hochschild Mining (HOC) 477.40p -2.27%Talvivaara Mining Company (TALV) 262.00p -2.24%Invensys (ISYS) 205.10p -2.24%