(ShareCast News) - London's FTSE 250 index was down 2.3% to 15,741.87 at 1430 GMT, tracking the broader market as worries about Chinese growth and sliding oil prices kept investors on edge.JD Wetherspoon was the worst performer after the pub group said like-for-like sales improved in the first 12 weeks of the second quarter but warned that operating margins would be 1.1% lower than the same period last year due to increased labour costs.Chairman Tim Martin said his current view was that profits for this year were "likely to be towards the lower end of analysts' expectations".Challenger bank OneSavings was in the red after Credit Suisse initiated coverage of the stock at 'underperform' with a 315p price target, saying it is too dependent on buy-to-let to achieve medium-term customer loan growth targets of around 20%."Implied 34% over 2014-18E annual BTL growth looks very ambitious versus growth achieved by other BTL lenders in the pre-financial crisis boom, when the overall market was growing more than twice as fast," it said.On the upside, stationer and newsagent WH Smith was the standout gainer after it said sales from its shops at airports and train stations were up 5% in the 20 weeks to 16 January, although High Street sales were flat over the period.In addition, Chief executive Stephen Clarke said full year profit growth was expected to be "slightly ahead of plan" as overall group sales rose 4% and 2% on a like-for-like basis.The stock was also supported by a research note from Peel Hunt, which upped its rating to 'buy' from 'add' and lifted the price target to 1,800p from 1,680p."A very pleasant surprise from WH Smith: LFL trading on the High Street is in positive territory for the first time in at least a decade, and Travel retains its momentum: there's a decent upgrade here and with a demerger a distinct possibility, the shares are cheap," it said.Pet supplies retailer Pets at Home was also in the black after posting slightly better-than-expected sales for the third quarter, along with a rise in total revenue growth.For the three months to the end of December, like-for-like sales increased 2.2% compared with the same period the previous year and slightly exceeding analysts' expectations for a 2.1% rise.Pets at Home reported total revenue growth of 7.1% to £195.1m, with merchandise revenue up 5.4% to £177.3m and services revenues up 27.4% to £17.8m.RisersWH Smith (SMWH) 1,699.00p 6.99%Pets at Home Group (PETS) 241.20p 3.43%Ocado Group (OCDO) 267.00p 3.05%Vedanta Resources (VED) 218.00p 1.68%Zoopla Property Group (WI) (ZPLA) 202.60p 1.20%Drax Group (DRX) 214.50p 1.18%Tate & Lyle (TATE) 596.00p 0.93%Polymetal International (POLY) 531.50p 0.66%John Laing Infrastructure Fund Ltd (JLIF) 116.90p 0.34%HICL Infrastructure Company Ltd (HICL) 151.90p 0.26%FallersWetherspoon (J.D.) (JDW) 616.00p -8.67%Nostrum Oil & Gas (NOG) 305.00p -6.78%IP Group (IPO) 169.10p -6.73%Morgan Advanced Materials (MGAM) 200.60p -6.44%OneSavings Bank (OSB) 294.30p -5.97%Amec Foster Wheeler (AMFW) 359.00p -5.90%Jardine Lloyd Thompson Group (JLT) 804.00p -5.85%Aveva Group (AVV) 1,324.00p -5.83%Jimmy Choo (CHOO) 122.50p -5.77%International Personal Finance (IPF) 230.20p -5.66%