Top shares rose on Wednesday after earnings from consumer technology bellwether Apple
But UK fourth-quarter GDP figures, due at 0930 GMT, were seen tempering enthusiasm.
The growth numbers are expected to show that Britain's economy contracted at the end of last year, pointing towards a mild recession and setting the stage for further stimulus by the Bank of England.
Chip designer ARM Holdings
It reads positively for ARM, said Didier Scemama at RBS.
Apple is not the only customer of ARM -- they supply virtually every smartphone and tablet with their cheap designs -- but from a sentiment standpoint there has been a strong correlation between the two share prices.
The UK benchmark index <.FTSE> was up 3.34 points, or 0.1 percent, at 5,755.24 by 0918 GMT, having dipped 0.5 percent on Tuesday.
Investors were bullish ahead of the conclusion of a two-day policy meeting of the U.S. Federal Open Market Committee, expected to result in forecasts showing interest rates will be near zero for at least two more years.
If rates are kept at zero for a long time, investors have little option but to put money into interest-generating assets such as equities, because money kept in the bank is eroded by inflation, said Manoj Ladwa, senior trader at ETX Capital.
And it's not necessarily always the case that they will just buy into U.S. equities. That money does slosh around the global economy and some of it will filter over here as well.
Mining stocks <.FTNMX1770> added the most weight to the FTSE 100's gains, tracking an advance in key base metals prices, on hopes a potential boost to U.S. infrastructure spending will help the demand picture for raw materials.
In his State of the Union address, U.S. President Barack Obama proposed to divert half the money America will save from the end of its wars in Iraq and Afghanistan into high-speed rail lines and repairs to the nation's roads and infrastructure.
Weakness among banks <.FTNMX8350> countered these gains, as worries about Greece potentially facing a messy default prompted further profit taking in the sector which has risen 13.6 percent this year, against a 3.2 percent rise on the FTSE 100.
Royal Bank of Scotland
While the UK market has kicked off 2012 on a bullish note, some investors were less than upbeat, citing concerns over the European sovereign debt crisis.
The theme so far this year has been buying the underperformers of last year on the hope that the global economy, and especially China and Europe, have seen the bottom,
said Lex van Dam, hedge fund manager at Hampstead Capital, which manages $500 million of assets.
I would personally not chase it.
(Additional reporting by Paul Sandle; Editing by David Holmes)