UK stocks were in positive territory in early trading on Tuesday though gains were only slight with markets cautious ahead of the all-important monetary policy meeting in the States.The two-day Federal Open Market Committee meeting which concludes tomorrow will likely keep upside on markets limited over the next two sessions with investors refraining from taking too much risk in case of a negative surprise.Wall Street benchmarks were volatile by the close of trade last night, finishing well below their intraday highs, after the Financial Times suggested that Fed Chairman Ben Bernanke is likely to signal tomorrow that the central bank is close to tapering its $85bn-a-month in asset purchases."Once markets had determined it was simply an opinion piece and there was nothing new in it they managed to recover enough to still close higher, but the entire sorry episode signifies how reliant on central-bank stimulus markets have become," said Senior Market Analyst Michael Hewson from CMC Markets. "We hear an awful lot about how stocks are so cheap yet the mere prospect of the slowing down of stimulus measures is enough to send markets into a tailspin. They can't be that cheap then, that investors are able to feel comfortable buying them, unless there is a Fed comfort blanket backstopping them?" Several key economic indicators are out in the UK this morning, including the consumer price index, the producer price index and real price index. Over in Germany, there'll be the latest release of the ZEW economic sentiment survey, while in the States, eyes will be on the US Aconsumer price index, building permits and housing starts.Whitbread, RSA and HSBC provide a liftUK hotel and restaurant group Whitbread gained after reporting a 3.1% rise in total like-for-like sales for the 13 weeks to May 30th, as strong growth at Costa outweighed a more subdued performance elsewhere.RSA Insurance was a high riser this morning after Credit Suisse upgraded the stock from 'neutral' to 'outperform'. The broker said: "We believe the multitude of factors that have weighed on returns at RSA will abate over the next two years, leading to an upswing in reported earnings."HSBC was also benefitting from an upgrade after Citigroup raised its rating from 'neutral' to 'buy' following recent underperformance.In contrast, security solutions group G4S was firmly in the red after Goldman Sachs reiterated its 'conviction sell' recommendation and cut its target price for the stock on the back of emerging-market FX weakness.Temporary power and temperature control supplier Aggreko fell after an in-line performance in the first half, though trading in its two main divisions still remains mixed - the Local business continues to grow strongly while Power Projects growth was subdued.Beverage giant SABMiller rose on the news that itself and Kopparberg Brewery AB have entered into a co-operation agreement for the long-term licensing of Kopparberg cider products in certain selected markets. On the FTSE 250, translation and communications software firm SDL plummeted after cutting its outlook for the current financial year following a first-half performance that was below management expectations. Profit before tax and amortisation is now expected to be within the range £15-20m in 2013 compared to £35.5m in 2012.FTSE 100 - RisersWhitbread (WTB) 3,041.00p +3.97%RSA Insurance Group (RSA) 120.00p +1.87%Bunzl (BNZL) 1,294.00p +1.81%Petrofac Ltd. (PFC) 1,310.00p +1.71%Lloyds Banking Group (LLOY) 62.27p +1.58%Croda International (CRDA) 2,426.00p +1.55%Schroders (SDR) 2,212.00p +1.47%Hargreaves Lansdown (HL.) 920.50p +1.43%BT Group (BT.A) 316.40p +1.41%Meggitt (MGGT) 525.50p +1.35%FTSE 100 - FallersG4S (GFS) 239.20p -2.29%Aggreko (AGK) 1,753.00p -2.12%Eurasian Natural Resources Corp. (ENRC) 238.00p -0.96%BHP Billiton (BLT) 1,799.00p -0.91%CRH (CRH) 1,325.00p -0.67%Shire Plc (SHP) 2,082.00p -0.62%GlaxoSmithKline (GSK) 1,678.00p -0.47%Kingfisher (KGF) 352.20p -0.42%Fresnillo (FRES) 1,093.00p -0.36%Evraz (EVR) 118.80p -0.34%FTSE 250 - RisersAveva Group (AVV) 2,408.00p +6.93%Supergroup (SGP) 708.50p +3.43%Computacenter (CCC) 459.30p +3.21%TalkTalk Telecom Group (TALK) 231.50p +3.12%Hiscox Ltd (HSX) 548.00p +2.72%Telecity Group (TCY) 944.50p +2.50%Intermediate Capital Group (ICP) 450.20p +2.36%Kenmare Resources (KMR) 29.41p +2.30%Ashtead Group (AHT) 629.50p +2.27%Heritage Oil (HOIL) 147.50p +2.22%FTSE 250 - FallersSDL (SDL) 261.00p -32.47%Chemring Group (CHG) 247.90p -6.70%Vesuvius (VSVS) 370.70p -1.98%Rank Group (RNK) 150.10p -1.90%Enterprise Inns (ETI) 106.90p -1.47%Betfair Group (BET) 815.00p -1.21%Greene King (GNK) 788.50p -1.19%Dialight (DIA) 1,117.00p -1.15%Home Retail Group (HOME) 130.70p -0.98%Brewin Dolphin Holdings (BRW) 230.00p -0.73%