London open: Markets edge lower on mixed corporate updates

- RSA, G4S lead losses after updates- Shire, M&S provide some support to markets- Economic data in focustechMARK 2,650.20 -0.04%FTSE 100 6,755.11 -0.13%FTSE 250 15,451.03 -0.11%UK markets opened slightly lower on Tuesday as investors digested a raft of mixed corporate updates from some heavyweight stocks in London.RSA Insurance was a heavy faller early on after saying it was hit by losses related to "severe weather" so far this year, while G4S fell after unveiling plans to restructure; Associated British Foods, Legal & General and Imperial Tobacco also failed to impress with their results.On the upside, Shire rose after positive drug tests and Marks & Spencer's first-half figures came in better than expected; mining stocks were also registering decent gains early on.The focus now turns to economic data due for release later on, including the UK services purchasing managers' index for October which is expected to fall slightly from 60.3 to 60. Eurozone producer price inflation figures are also on the agenda today, along with the ISM non-manufacturing index in the States this afternoon. Increased speculation over an imminent European Central Bank (ECB) rate cut boosted markets on Monday. However, Chief Market Analyst Michael Hewson from CMC Markets said that such a move is unlikely given that the ECB has "always been a conservative central bank". He said: "Any reaction this week to last week's data would be highly unusual, and could well be interpreted as a knee-jerk reaction to one or two pieces of data. It seems more likely that we may get some action in December, which may be flagged up at the press conference on Thursday."Meanwhile, chatter surrounding an impending scaling back of stimulus by the Federal Reserve continues to be closely watched ahead of Friday's all-important jobs report. Analysts are estimating a meagre 125,000 increase in non-farm payrolls in October, well below the 148,000 gain the month before. RSA drops as weather dents resultsRSA fell sharply this morning after saying that recent storms and heavy winds now mean that weather-related losses will be "materially above planning assumptions" in 2013. The company has now said that its full-year return on equity will be below 10%.Security group G4S, which is being investigated by the Serious Fraud Office over a government contract, declined after saying that has identified 35 businesses to grow or restructure. AB Foods was also lower despite delivering a better-than-expected set of annual results following a strong performance from Primark and an improvement in Grocery. Insurance firm Legal & General also underwhelmed with its third-quarter results even though worldwide sales came in ahead of forecasts. Imperial Tobacco Group saw its annual tobacco revenue fall 1% to £20.8bn as volumes declined 7%.On a brighter note, drug developer Shire reported positive results for its Binge Eating Disorder (BED) treatment, Vyvanse, causing shares to rise this morning. M&S meanwhile saw underlying pre-tax profit fall 8.9% to £261.6m in the first half of the year, though this was not as bad as many analysts were expecting.Mining stocks were also doing their best to support markets this morning with Anglo American, Rio Tinto, BHP Billiton, Fresnillo, Glencore Xstrata and Antofagasta all registering decent gains.FTSE 100 - RisersAnglo American (AAL) 1,537.00p +2.84%Marks & Spencer Group (MKS) 497.40p +2.11%Glencore Xstrata (GLEN) 342.15p +2.01%BHP Billiton (BLT) 1,986.50p +1.90%Imperial Tobacco Group (IMT) 2,349.00p +1.69%Fresnillo (FRES) 1,017.00p +1.60%Shire Plc (SHP) 2,858.00p +1.35%Rio Tinto (RIO) 3,332.50p +1.31%Vedanta Resources (VED) 1,099.00p +1.10%Antofagasta (ANTO) 872.00p +0.98%FTSE 100 - FallersRSA Insurance Group (RSA) 122.40p -5.19%G4S (GFS) 245.40p -3.39%Royal Bank of Scotland Group (RBS) 320.60p -3.35%Associated British Foods (ABF) 2,184.00p -3.15%Legal & General Group (LGEN) 214.10p -1.74%Lloyds Banking Group (LLOY) 75.94p -1.43%Persimmon (PSN) 1,252.00p -1.18%Aviva (AV.) 441.70p -1.16%Old Mutual (OML) 200.40p -1.13%Admiral Group (ADM) 1,262.00p -1.10%FTSE 250 - RisersKazakhmys (KAZ) 269.90p +4.05%Lonmin (LMI) 333.60p +2.49%IP Group (IPO) 150.00p +2.04%Ferrexpo (FXPO) 193.00p +1.95%Polymetal International (POLY) 582.00p +1.84%Kenmare Resources (KMR) 22.26p +1.83%PayPoint (PAY) 1,020.00p +1.69%RPC Group (RPC) 516.00p +1.67%Synthomer (SYNT) 237.00p +1.54%BlackRock World Mining Trust (BRWM) 491.60p +1.47%FTSE 250 - FallersCSR (CSR) 516.00p -5.49%Rank Group (RNK) 143.30p -2.72%Telecity Group (TCY) 725.00p -2.03%Diploma (DPLM) 672.50p -1.97%Centamin (DI) (CEY) 50.40p -1.95%Barratt Developments (BDEV) 329.40p -1.88%Drax Group (DRX) 637.50p -1.70%Taylor Wimpey (TW.) 109.10p -1.53%Berkeley Group Holdings (The) (BKG) 2,297.00p -1.46%Wetherspoon (J.D.) (JDW) 722.00p -1.43%BC