London markets hit a five-month low on Wednesday, driven by continued Greece concerns, a sell-off in Chinese markets and weakness in the mining, construction and technology sectors.As of 14:00 BST, the FTSE 100 was trading 0.42% lower at 6,683.British American Tobacco and Imperial Tobacco led the risers, as Credit Suisse reinstated coverage on both stocks at 'outperform'. The broker applauded BAT's "consistent track record" and showed optimism about Imperial's recent purchase of Reynolds assets.National Grid was also boosted by positive broker sentiment, as Morgan Stanley upgraded its rating on the stock to 'overweight' from 'equalweight' and raised its price target on the shares to 955p from 910p saying it sees attractions in all three business areas.GlaxoSmithKline was up on rumours it could become the latest takeover target in the sector. According to the Daily Mail, market participants are speculating that the company may face an approach from Switzerland's Roche or US company Johnson & Johnson at about 1900p per share.Standard Chartered extended Tuesday's losses, which came as Jefferies cut its price target from 722p to 656p and warned the company may cut its dividend to bolster capital.Mining stocks were among the worst performers, with Rio Tinto, Randgold Resources and Antofagasta all in negative territory.Royal Mail was in the red after Ofcom announced a fundamental review to make sure the postal operator faces adequate competition following Whistl's withdrawal from the direct-delivery letters market.Leisure group Whitbread fell after missing forecasts slightly with a first-quarter update. Like-for-like sales rose by 4.3% as a flat performance in the restaurants division limited growth.Shares of industrial equipment hire company Ashtead dipped after underwhelming investors with its with full-year results. The group posted a 33% rise in full-year pre-tax profit to £473.8m on strong US and UK markets.RisersBritish American Tobacco (BATS) 3,500.50p +2.61%Imperial Tobacco Group (IMT) 3,229.00p +1.70%GlaxoSmithKline (GSK) 1,364.50p +1.00%Aberdeen Asset Management (ADN) 411.80p +0.96%Centrica (CNA) 264.10p +0.80%Barratt Developments (BDEV) 600.00p +0.67%Vodafone Group (VOD) 232.50p +0.56%Taylor Wimpey (TW.) 184.30p +0.49%National Grid (NG.) 852.40p +0.45%SABMiller (SAB) 3,310.50p +0.33%FallersAshtead Group (AHT) 1,091.00p -3.19%International Consolidated Airlines Group SA (CDI) (IAG) 494.80p -2.69%Antofagasta (ANTO) 710.50p -2.40%Anglo American (AAL) 974.00p -2.05%Randgold Resources Ltd. (RRS) 4,536.00p -1.95%Glencore (GLEN) 273.25p -1.80%Rio Tinto (RIO) 2,756.50p -1.78%Standard Chartered (STAN) 1,021.50p -1.59%Royal Dutch Shell 'A' (RDSA) 1,826.00p -1.54%TUI AG Reg Shs (DI) (TUI) 1,153.00p -1.54%