UK equities pushed into positive territory (albeit only slightly) by midday but trade was choppy in the morning session, as a Standard & Poor's warning over Eurozone ratings rattled markets' nerves.Nevertheless, US futures were pointing to a positive start on Wall Street, providing a lift here in London.In other news, the UK housing market continued its bumpy ride as prices fell 0.9% between October and November, according to figures from the Halifax.S&P WARNS OF MASS EUROZONE DOWNGRADE Reports of a impending credit rating agency action on the Eurozone were confirmed last night as S&P announced that it placed the rating of 15 of the area's sovereigns on CreditWatch with a negative outlook. Only Greece (whose rating was already at CC categorized as "highly vulnerable, speculative bonds" with a high near-term probability of default) and Cyprus (whose rating was already on review) escaped this ratings action. S&P explained that these "CreditWatch placements are prompted by our belief thatsystemic stresses in the euro zone have risen in recent weeks to the extent that they now put downward pressure on the credit standing of the euro zone as a whole." France is the country which is facing the most severe warning, with S&P saying Europe's second largest economy could be downgraded two notches unless it improves its budgetary position. France's finance minister Francois Baroin is reported by Reuters to have already ruled out more cuts. He argues that S&P has not taken account of yesterday's agreement between Sarkozy and Chancellor Angela Merkel of Germany to centralise Eurozone budget planning. WOLSELEY RISES AFTER Q1 RESULTS, MEGGITT LOWER AFTER DOWNGRADEWolseley, the FTSE 100 distributor of plumbing and heating products, led the risers all morning after seeing like-for-like revenue growth of 5% in the three months to the end of October, compared to the same period of 2010.Meggitt was trading lower by midday after Credit Suisse downgraded its rating from outperform to underperform, cutting the target price from 410p to 330p. "Whilst we expect robust FY2011 results, we are cautious on Meggitt's civil aftermarket and military end-markets in 2012/13," analysts said.Shire was being helped higher as Goldman Sachs reiterated its buy recommendation on the pharmaceuticals giant. Sector peer GlaxoSmithKline was also in demand.After initially falling into the red, along with the broader mining sector, Xstrata was registering small gains by lunchtime after it reported "significant increases" to its total mineral resources at the Las Bambas and Corroccohuayco projects in southern Peru and at El Pachón in Argentina.Meanwhile, banks were mixed, with HSBC and Barclays falling and Lloyds and RBS rising.Utilities were dominating the fallers list, with United Utilities, SSE, International Power and Centrica providing a drag.On the FTSE 250, Electra Private Equity was the best performer after the investment trust saw an 8.5% rise in net asset value (NAV) per share after a strong portfolio performance during the year ended 30 September.RETAILERS SOLD OFFConsumers are keeping "a tight rein on their spending, despite Christmas being so near", according to the British Retail Consortium (BRC). Total sales were up 0.7%, against a 2.8% increase in November 2010, the retailers' lobby group said.Retailers were among the worst performers of the day, with blue chips Next and Marks & Spencer weighing on the Footsie, and mid-cap stocks Home Retail and Dunelm falling on the FTSE 250.OTHER MARKETSBrent Crude for January delivery had climbed 0.25% at 11:50 in London to $110.08 per barrel.Gold futures were trading down 0.65% at $1,723 per ounceBCFTSE 100 - RisersWolseley (WOS) 1,972.00p +3.63%Lloyds Banking Group (LLOY) 27.80p +2.96%Sage Group (SGE) 293.60p +2.16%GlaxoSmithKline (GSK) 1,422.00p +1.61%Shire Plc (SHP) 2,135.00p +1.09%Imperial Tobacco Group (IMT) 2,329.00p +1.09%Aggreko (AGK) 1,892.00p +1.01%Rolls-Royce Group (RR.) 721.00p +0.98%Compass Group (CPG) 591.50p +0.94%Rexam (REX) 351.80p +0.92%FTSE 100 - FallersAdmiral Group (ADM) 899.00p -3.07%Marks & Spencer Group (MKS) 320.70p -2.52%Vedanta Resources (VED) 1,086.00p -2.25%Next (NXT) 2,603.00p -2.14%United Utilities Group (UU.) 602.50p -2.11%Centrica (CNA) 287.70p -1.84%British Sky Broadcasting Group (BSY) 745.00p -1.78%Fresnillo (FRES) 1,727.00p -1.71%International Power (IPR) 328.80p -1.62%Meggitt (MGGT) 377.80p -1.49%FTSE 250 - RisersElectra Private Equity (ELTA) 1,475.00p +3.51%Interserve (IRV) 329.20p +2.84%Thomas Cook Group (TCG) 17.00p +2.35%Carpetright (CPR) 475.70p +2.04%Domino Printing Sciences (DNO) 518.00p +1.87%Premier Foods (PFD) 5.70p +1.79%Yule Catto & Co (YULC) 176.90p +1.73%Personal Assets Trust (PNL) 33,900.00p +1.68%Stagecoach Group (SGC) 247.60p +1.56%William Hill (WMH) 203.50p +1.45%FTSE 250 - FallersPace (PIC) 63.85p -5.96%Home Retail Group (HOME) 95.00p -5.85%Elementis (ELM) 140.60p -4.35%Centamin Egypt Ltd. (CEY) 96.00p -4.00%Victrex (VCT) 1,147.00p -3.78%Dunelm Group (DNLM) 438.60p -3.46%Hays (HAS) 68.30p -3.33%Daejan Holdings (DJAN) 2,620.00p -3.29%Premier Farnell (PFL) 179.50p -3.18%New World Resources A Shares (NWR) 457.50p -3.07%