Markets opened slightly lower in London on Thursday despite a much-welcome boost for the Japanese economy announced overnight, as investors kept their powder dry ahead of policy decisions from the Bank of England (BoE) and the European Central Bank (ECB) this afternoon.The Bank of Japan (BoJ) announced an aggressive monetary stance as its new Governor Haruhiko Kuroda took the helm determined to fight deflation. The BoJ left rates untouched at record lows but indicated that it would pursue quantitative easing as long it was necessary in order to achieve its 2.0% inflation target. With regard to asset purchases, the BoJ plans to double its holdings and said it was likely to buy 7.0trn yen in long-term Japanese government bonds each month. Tokyo's benchmark, the Nikkei, ended trading overnight up 2.2%.BoE and ECB in focusThe BoE decision is due out at midday with the ECB announcement shortly after, though both parties are expected to stand pat. However, investors will be watching the press conference with ECB President Mario Draghi closely for any hints of a rate cut some time in the future given the recent poor run of economic data, political uncertainty in Italy and fragile conditions in Cyprus.Market Strategist Ishaq Siddiqi from ETX Capital said: "Some believe [Draghi] may be under pressure to consider multiple options such as another round of long-term refinancing operations, interest rate cuts and encourage lending to corporates in the region to ease liquidity conditions. Much of the questions in the Q&A press conference post the rate call will be about Cyprus and Italy."Also on tap for markets to digest will be purchasing managers' indices (PMIs) for the service sectors in the UK and Eurozone."Cautious start for European stock markets this morning with investors reluctant from building risk exposure ahead of central bank meetings from the BoE and ECB together with PMI services data from the region before that," Siddiqi said.FTSE 100: Miners rebound after recent weaknessMining stocks such as ENRC, EVRAZ and Polymetal were making gains early on, recovering after their recent falls. Vedanta was a high riser, extending gains made yesterday after the High Court of Bombay at Goa approved the group's restructuring. While final approval from the Madras High Court is still needed, Credit Suisse reiterated its 'outperform' rating on the stock this morning, saying: "The group simplification and deleveraging path is now close to fruition and this remains a key element of our investment case."Property giant British Land rose after buying out joint-venture partner Tesco in the Surrey Quays Shopping Centre in an attempt to accelerate its investment programme in London and the South East. AMEC, the consultancy, engineering and project management outfit, was higher after reporting that the order book edged higher in the first quarter, giving it good visibility for 2013 and beyond.IAG was subdued after saying that it has signed a deal for 18 of Boeing's 787 Dreamliners to upgrade its British Airways fleet.FTSE 250: Domino's, BTG among the risers early onDomino's Pizza jumped early on after delivering some tasty first-quarter number, with like-for-like sales up 6.6% trances to new products such as its Hot Dog Stuffed Crust.Healthcare group BTG was also sharply higher after upwardly revising its revenue forecast for the full year ended March 31st.FTSE 100 - RisersEurasian Natural Resources Corp. (ENRC) 247.40p +10.15%Vedanta Resources (VED) 1,042.00p +3.27%Johnson Matthey (JMAT) 2,333.00p +2.10%Evraz (EVR) 207.70p +2.06%Petrofac Ltd. (PFC) 1,442.00p +1.69%Amec (AMEC) 1,096.00p +1.58%Xstrata (XTA) 1,061.00p +1.53%Royal Bank of Scotland Group (RBS) 275.20p +1.51%Rio Tinto (RIO) 3,069.50p +1.49%BHP Billiton (BLT) 1,927.00p +1.42%FTSE 100 - FallersARM Holdings (ARM) 899.00p -1.86%Marks & Spencer Group (MKS) 386.70p -1.35%Reed Elsevier (REL) 779.50p -1.27%ITV (ITV) 127.50p -1.24%Aberdeen Asset Management (ADN) 422.20p -1.22%Next (NXT) 4,344.00p -1.21%Randgold Resources Ltd. (RRS) 5,310.00p -1.21%InterContinental Hotels Group (IHG) 1,989.00p -1.19%Reckitt Benckiser Group (RB.) 4,721.00p -1.11%Carnival (CCL) 2,243.00p -1.10%FTSE 250 - RisersDomino's Pizza Group (DOM) 608.00p +6.48%Kazakhmys (KAZ) 371.00p +5.79%BTG (BTG) 374.80p +4.52%ITE Group (ITE) 288.20p +3.45%International Personal Finance (IPF) 465.60p +2.28%SDL (SDL) 418.00p +2.23%Cairn Energy (CNE) 280.20p +1.63%Rank Group (RNK) 160.90p +1.51%Anite (AIE) 125.70p +1.45%NMC Health (NMC) 317.00p +1.44%FTSE 250 - FallersHeritage Oil (HOIL) 160.00p -9.91%WH Smith (SMWH) 732.50p -4.12%TalkTalk Telecom Group (TALK) 263.00p -2.66%Ocado Group (OCDO) 144.50p -2.56%Interserve (IRV) 477.80p -2.35%Senior (SNR) 245.10p -2.27%Synthomer (SYNT) 208.90p -2.15%Moneysupermarket.com Group (MONY) 196.40p -2.04%Supergroup (SGP) 631.00p -2.02%Fidessa Group (FDSA) 1,903.00p -1.91%BC