The BoJ joined in recent action from the United States and Europe with bond purchases designed to kick-start its economy as central banks aim to halt the slowdown in global growth and take the sting out of the euro zone debt crisis.

As long as they keep pumping money into the market, then it's all positive and to the good. But we have the situation that whatever they do is only ever a sticking plaster, it's never a fix, so while equities in my view continue to look cheap despite the fact they have risen ... we need to be reading the small print, said David Battersby, an investment manager at Redmayne-Bentley Stockbrokers.

Gains by banks provided the biggest lift for the blue chips, with global heavyweight HSBC the best sector performer, ahead 1.7 percent and alone adding over 7 points to the index in volume of 120 percent of its 90-day daily average. FTSE 100 volume was at 85 percent of the daily average.

HSBC and other banks benefited from price target hikes by BofA Merrill Lynch in a review of European Banks which concluded that moves by central bank policymakers have reduced the likelihood of negative risk events for the sector.

To reflect this fall in equity risk premium, Merrill has rolled forward its methodology to a 2013 valuation, leading it to raise targets in the sector by nearly 9 percent on average.

But the bank said while it believes policymaker actions have significantly reduced risks, it does not believe they do much to change the dull, short-term macro economic outlook.

Bank of England policymakers judged Britain's short-run inflation outlook had darkened earlier this month, but some still thought they would probably need to inject more stimulus into the economy, minutes of their September meeting showed on Wednesday.

The FTSE 100 closed up 20.32 points, or 0.4 percent at 5,888.48 on Wednesday, holding near six-month highs reached last Friday following U.S. Federal Reserve stimulus moves.

Strength in energy and mining <.FTNMX1770 stocks also gave support to the blue chips, with the sectors bolstered by hopes that the central bank stimulus moves will help boost demand for oil and metals, especially if China joins in.

From a domino perspective everyone will look towards China. They haven't moved on any interest rate cuts for a number of months now, and we know they are already feeling the pressure in terms of slowing growth. They have already given indications that they are looking to act and they have the resources to do so, said Joshua Raymond, Chief Market Strategist at City Index.

I guess it is just now trying to pull the pieces together with the Fed doing it, the ECB, BoE and the Bank of Japan now, so most people are looking towards China, and that could really give further support to the FTSE considering the heavyweight bearing the miners have for the index, Raymond added.

GO UU

United Utilities (UU) was a top individual FTSE 100 gainer, up 2.8 percent with traders citing rehashed bid talk ahead of a trading update from the water firm due on Thursday.

Several papers said a Middle East sovereign wealth fund might be willing to pay up to 950 pence-per-share for UU.

I would be involved in defensive stocks. So I am quite happy with UK utility stocks, although some of them are looking toppy at the moment, said Redmayne's Battersby, I am also a big fan of tobacco stocks.

Tobacco stocks were, however, lower, with Imperial Tobacco losing 1.1 percent ahead of a trading update due on Thursday.

Aviva was the worst blue chip performer, off 3.3 percent, having dropped on Tuesday in reaction to two broker downgrades on valuation grounds, as the stock traded with investors no longer qualifying for the latest dividend payout.