UK stocks jumped on Monday morning despite ongoing uncertainty about Greece, as the mood on the market was boosted by bid speculation surrounding Aveva and Bwin.party.The FTSE 100 was up 0.56% at 6,999.75 early on, with mining stocks leading the charge, though BHP Billiton was bucking the trend.Economic data is on the thin side on Monday with the NAHB US housing market index at 15:00 the only major release.Oanda analyst Craig Erlam said the positive open across Europe "suggest[ed] a more positive sentiment among traders despite Greece's apparent insistence on walking blindly towards default without any consideration for the consequences".It emerged over the weekend that Greek prime minister Alexis Tsipras had written to the IMF saying it did not have enough funds to repay it. While the repayment was actually made last week using emerging cash reserves, Tsipras stressed that Athens would not "back down on pension and labour issues" as creditors continue to negotiate over a cash-for-reforms deal.Erlam said: "If neither side changes its stance then it would appear Greece is only a couple of weeks from defaulting on its debt and yet, the markets seem rather unfazed. Maybe investors have become immune to all this tough talk and still think Tsipras will cave or resign, enabling a late deal to be done. If we remain in this position as we near the 5 June, I doubt investors will be so confident."Aveva and Bwin surgeEngineering software group Aveva was making decent gains early on after weekend reports that it could be an acquisition target of Schneider Electric, General Electric and Emerson Electric.Meanwhile, online gaming group Bwin.Party Digital Entertainment jumped after confirming it has received a cash and shares bid from sector peer 888 Holdings.Mining stocks were mostly higher, including Randgold Resources, Fresnillo, Anglo American, Rio Tinto and Glencore.Fresnillo said it remains on track to hit its output guidance in 2015 after a strong start to the year, while Rio was making headlines on rumours it could raise $1bn from the sale of some aluminium assets.However, BHP Billiton was trading with heavy losses after its South32 spin-off was valued at the lower end of market expectations on its debut on the Australian Stock Exchange.Babcock gained after posting a 47% rise in pre-tax profit for the year ended March 31st to £313.1m on revenues up 37% at £4.5bn. The company said that revenue growth has come both organically, through major contract wins and by expanding and enhancing existing contracts, as well as from acquisitions made in the past year.Weir was a top riser after analysts at Citigroup upgraded the stock to 'buy', while Coca-Cola HBC and Lloyds were hit by downgrades at Deutsche Bank and and Investec, respectively.Market MoverstechMARK 3,255.95 +0.53%FTSE 100 6,999.75 +0.56%FTSE 250 18,059.03 +0.21%FTSE 100 - RisersFresnillo (FRES) 777.50p +3.39%Weir Group (WEIR) 1,955.00p +3.00%Sage Group (SGE) 557.50p +2.48%Royal Mail (RMG) 495.70p +2.12%Marks & Spencer Group (MKS) 578.50p +1.85%Randgold Resources Ltd. (RRS) 4,958.00p +1.85%Taylor Wimpey (TW.) 187.90p +1.73%GKN (GKN) 359.80p +1.70%Glencore (GLEN) 297.50p +1.43%Centrica (CNA) 284.90p +1.39%FTSE 100 - FallersBHP Billiton (BLT) 1,465.50p -4.40%Intertek Group (ITRK) 2,673.00p -0.82%Coca-Cola HBC AG (CDI) (CCH) 1,382.00p -0.65%Lloyds Banking Group (LLOY) 88.43p -0.64%Hikma Pharmaceuticals (HIK) 2,088.00p -0.62%Aviva (AV.) 540.50p -0.37%Aberdeen Asset Management (ADN) 432.00p -0.35%easyJet (EZJ) 1,698.00p -0.12%Experian (EXPN) 1,225.00p -0.08%FTSE 250 - RisersAveva Group (AVV) 1,976.00p +7.68%Bwin.party Digital Entertainment (BPTY) 106.20p +6.79%Mitie Group (MTO) 295.90p +2.85%Kier Group (KIE) 1,358.00p +2.56%AL Noor Hospitals Group (ANH) 864.00p +2.49%Crest Nicholson Holdings (CRST) 517.50p +2.27%Centamin (DI) (CEY) 67.30p +2.20%Ladbrokes (LAD) 119.40p +1.79%Acacia Mining (ACA) 314.00p +1.78%Polymetal International (POLY) 561.50p +1.72%FTSE 250 - FallersPremier Oil (PMO) 171.50p -3.22%Inmarsat (ISAT) 964.00p -3.16%Laird (LRD) 368.90p -2.66%Saga (SAGA) 204.50p -2.57%Thomas Cook Group (TCG) 157.80p -2.17%Nostrum Oil & Gas (NOG) 561.50p -2.01%Essentra (ESNT) 986.50p -1.94%Diploma (DPLM) 795.00p -1.91%Cranswick (CWK) 1,560.00p -1.76%Fidessa Group (FDSA) 2,307.00p -1.24%