- IIF warns of fall-out in case of Greek default.- Polymetal leads miners lower, Fresnillo bucks trend after results.- Centamin plummets after halting operations at Sukari.The FTSE 100 was trading over a whole percentage point lower by midday as Greek default fears rattled the markets just two days before the crucial debt-swap deadline. Just a handful of blue chips were making gains, while the heavyweight mining sector was extending losses made yesterday when China cut its growth forecasts for 2012.Europe is awaiting a final decision this week on the Greek debt restructuring. Private investors have a March 8th deadline to decide if they will accept a debt exchange in which they will be required to take a 53.5% haircut in an agreement that would save Athens about €106bn (£88bn). However, the Institute of International Finance (IIF) - the group representing Greece's private creditors - has said that a disorderly Greek default would leave Italy and Spain in need of additional aid, taking the total amount of liabilities over the one trillion euro mark, Reuters reported this morning. In a document obtained by the news agency which was dated February 18th, the IIF said: "there are some very important and damaging ramifications that would result from a disorderly default on Greek government debt...It is difficult to add all these contingent liabilities up with any degree of precision, although it is hard to see how they would not exceed one trillion euros." ECONOMIC DATAThe value of UK retail sales fell by 0.3% on a like-for-like basis in February versus a year ago. On a total basis however - taking into account volumes - sales grew by 2.3%, above the 1.1% rate of growth seen in the same month of 2011, the BRC-KPMG sales monitor says.Meanwhile, UK house prices fell by 0.5% month-on-month (-1.9% year-on-year) during the month of February, to £160,118, according to the latest data from Halifax. The consensus estimate was for a rise of 0.3% month-on-month (-1.6% year-on-year).POLYMETAL LEADS MINERS LOWER AFTER DOWNGRADEMiners were among the worst performers in the opening hour in London, following yesterday's news that China expects its economy to grow by 7.5% in 2012 - set to be the first year of sub-8% growth in eight years. Mining stocks were down an average 1.24% by lunchtime today, with share prices standing over 8% lower than they were last Tuesday, on concerns that lower economic activity in the world's second-largest economy could dampen the demand for metals.Polymetal led the decline, dropping nearly 7%, after UBS downgraded its rating from buy to neutral and slashed its target price from 1,400p to 1,100p. Sector peers Evraz, ENRC and Kazakhmys were also registering heavy losses.Fresnillo, however, bucked the trend to trade higher after seeing sales rise by more than a half in 2011, helped by a surge in metals prices and an increase in production. Revenue in the 12 months ended December 31st increased by 55.6% from $1,409.6m to $2,192.7m. Meggitt, the engineering company focused on the aerospace, defence and energy markets, was a heavy faller despite seeing strong growth across all of its markets in 2011. Revenue in 2011 rose by a quarter to £1,455.3m from £1,162.0m in 2010, and roughly in line with market expectations of £1,458.7m. "In short, the 2011 result looks fine, but we harbour some reservations about the long-term outlook," said analysts at Jefferies. FTSE 250: CENTAMIN PLUMMETS ON ILLEGAL LABOUR UNRESTEgypt-focused gold miner Centamin took a tumble in late morning trade after announcing that it has temporarily halted operations at its flagship Sukari Gold Mine due to what it calls "illegal labour unrest". "The illegal unrest and work stoppage commenced as a result of a breakdown in on-going discussions involving general salary increases and other benefits with some members of the Sukari workforce," the firm said. Shares fell by as much as 16% on the news, but were trading around 9% down by noon.Oil group Exillon Energy was also a big mover, dropping nearly 6%, despite reporting a month-on-month increase in production at its main assets in Timan-Pechora and West Siberia.BCFTSE 100 - RisersHargreaves Lansdown (HL.) 457.20p +2.67%National Grid (NG.) 654.00p +0.77%Fresnillo (FRES) 1,845.00p +0.71%GlaxoSmithKline (GSK) 1,409.00p +0.36%British Sky Broadcasting Group (BSY) 684.00p +0.15%FTSE 100 - FallersPolymetal International (POLY) 945.00p -6.99%Evraz (EVR) 387.30p -4.42%Meggitt (MGGT) 382.90p -4.32%Eurasian Natural Resources Corp. (ENRC) 647.50p -4.07%Aviva (AV.) 353.10p -3.89%GKN (GKN) 206.50p -3.50%Cairn Energy (CNE) 320.50p -3.46%Wolseley (WOS) 2,340.00p -3.39%Intertek Group (ITRK) 2,295.00p -3.25%Barclays (BARC) 244.75p -3.22%FTSE 250 - RisersCape (CIU) 446.60p +4.01%Misys (MSY) 339.00p +1.19%AG Barr (BAG) 1,180.00p +1.03%Brewin Dolphin Holdings (BRW) 162.20p +0.75%BH Macro Ltd. USD Shares (BHMU) 19.74 +0.71%Supergroup (SGP) 518.50p +0.68%Ashtead Group (AHT) 258.60p +0.62%ITE Group (ITE) 229.70p +0.57%RIT Capital Partners (RCP) 1,206.00p +0.50%SVG Capital (SVI) 275.00p +0.44%FTSE 250 - FallersCentamin (DI) (CEY) 78.50p -9.25%Kenmare Resources (KMR) 50.50p -7.93%Exillon Energy (EXI) 208.10p -6.35%Afren (AFR) 125.50p -5.99%Cable & Wireless Worldwide (CW.) 31.52p -5.80%Michael Page International (MPI) 452.50p -5.53%New World Resources A Shares (NWR) 487.10p -5.05%International Personal Finance (IPF) 240.00p -4.76%Inchcape (INCH) 357.30p -4.21%Hays (HAS) 80.00p -4.19%