(ShareCast News) - Mid-caps edged lower on Wednesday, as gains in the construction and insurance sectors were eclipsed by weakness from technology, mining, engineering and oil stocks.As of 1600 BST, the FTSE 250 was trading 0.5% lower at 17,660.Mitchells & Butlers topped the risers after Numis raised its stance to 'add' from 'hold' following an 18% decline in the share price. "Following around 13% downgrades to our 2017E pre-tax profit forecasts to reflect the National Living Wage, there should be limited downside to forecasts, but medium-term upside if the company's operational efforts gain traction," the broker said.Tate & Lyle also benefited from favourale broker sentiment, after Goldman Sachs upgraded the stock to 'neutral' from 'sell' and raised its price target to 470p from 460p following its recent underperformance.Marston's was on the up as it said trading in the 10 months to July was positive and in line with expectations. In the 41 weeks to 18 July, like-for-like sales increased 1.7% year-on-year, with like-for-like food sales and like-for-like wet sales both rising 1.6% in the period.Croda International extended gains as Exane BNP Paribas upgraded the stock to 'neutral' from 'underperform' and raised its price target to 2,950p from 2,620p, noting the shares are close to fair value and pointing to potential catalysts such as M&A or a special dividend in the second half.TalkTalk slumped after it said the broadband market has become increasingly competitive and posted weaker-than-expected revenue growth for the three months to 30 June. In addition, the company struck a cautious note on the broadband market, saying it was softer than it has seen in recent quarters, with higher promotional activity in the sector.Acacia Mining, Evraz, Centamin and Kaz Minerals were trading in the red, as metal prices continued to dip across the board.