*BoE: Unemployment has risen markedly

*BoE: World activity continued to weaken, reflecting depressed confidence, persistent intl credit market problems

*BoE: To undertake a programme of asset purchases of GBP75 bln financed by the issuance of central bank reserves

*Pound surges against majors as BoE trims target rate to 0.50%; now worth 0.8889 against euro

*BoE Cuts Key Interest Rate To 0.5%