(ShareCast News) - London's FTSE 100 index was down 0.8% to 6,260.09 in afternoon trading, with miners pacing the decline.Heavily-weighted mining stocks were the worst performers as metals prices slipped, with Anglo American, BHP Billiton, Rio Tinto and Glencore all firmly on the back foot.Standard Chartered was down 5% ahead of its results of Tuesday, with investors fearing the worst. Citi analysts said they expect a "weak" quarter for the Asia-focused bank due to market volatility and a slowdown in China's economy, which could affect fee and trading income.On the upside, Imperial Brands, formerly known as Imperial Tobacco, was the standout gainer as Goldman Sachs upgraded the stock to 'buy' from 'neutral' following recent underperformance.It noted the shares are down 8% over the past month versus its European staples coverage and the broader market."Our 'buy' thesis is predicated on the company's highly cash-generative business model (we forecast over £13bn of free cash flow generation over the next 5 years, equivalent to 39% of its current market cap), attractive average EPS growth (7% pa) and dividend yield (c.5% pa) in CY17-18E," the bank said.Goldman said upcoming catalysts include the first half results on 4 May and the investor day on 8 June.Equipment rental firm Ashtead was also in the black after a double upgrade from Bank of America Merrill Lynch.The bank upped its stance on the stock to 'buy' from 'underperform' and boosted the target price to 1,100p from 800p, pointing to an improved outlook for the company's markets.Merrill Lynch raised its earnings per share estimates for 2017 and 2018 by 8% and 14%, highlighting improving economic indicators, increased capex expectations and a better outlook for rental yields.Housebuilders enjoyed another day of solid gains following an upgrade of Barratt Developments and Persimmon on Friday by Liberum, which said the valuations were now "much more accommodating". Market participants also attributed gains in the sector to the reduced probability of Brexit.Broadcaster ITV rose as investors snapped up some shares before the stock goes ex-dividend on Thursday to make the most of the 14.1p special dividend.RisersImperial Brands (IMB) 3,685.00p 3.18%Ashtead Group (AHT) 913.00p 2.58%Berkeley Group Holdings (The) (BKG) 2,960.00p 2.28%British Land Company (BLND) 700.00p 2.19%Intu Properties (INTU) 296.80p 2.17%ITV (ITV) 230.90p 1.90%Land Securities Group (LAND) 1,094.00p 1.86%Hammerson (HMSO) 580.00p 1.58%Persimmon (PSN) 1,921.00p 1.53%Taylor Wimpey (TW.) 178.10p 1.48%FallersAnglo American (AAL) 688.10p -6.10%Standard Chartered (STAN) 526.60p -5.32%BHP Billiton (BLT) 938.10p -5.01%Rio Tinto (RIO) 2,250.00p -3.62%Glencore (GLEN) 157.40p -2.72%Randgold Resources Ltd. (RRS) 6,390.00p -2.29%Royal Dutch Shell 'B' (RDSB) 1,787.00p -2.16%Royal Dutch Shell 'A' (RDSA) 1,778.50p -1.96%Prudential (PRU) 1,413.50p -1.84%Antofagasta (ANTO) 471.10p -1.81%