Profit-taking was in the air earlier in the session with the FTSE-100 Index at a five-month high, but it ended 8.2 points up at 6721.3 following the release of the data by the Office for National Statistics.
It showed UK gross domestic product (GDP) grew by 0.8% in the third quarter, the best performance since the second quarter of 2010. Elsewhere, markets in Europe and the US were quiet, with indices flat.
On the currency markets, the GDP figures - which were in line with expectations - failed to lift sterling, which was flat against the greenback at 1.62 US dollars and against the euro at 1.17 euros.
In London, there were gains for security companies G4S and Serco after senior management departures under efforts to rebuild their reputations following government contract scandals. FTSE-250 stock Serco announced group chief executive Christopher Hyman was stepping down less than a day after rival G4S revealed its UK and Ireland boss Richard Morris was leaving, to be replaced by Eddie Aston.
Serco rose nearly 1%, or 5p to 557.5p, as it also announced a restructure that will hive off its UK central government work from other public sector business, as well as a beefed up board and new code of conduct.
G4S, which was also benefiting from a broker upgrade, lifted 5.5p to 258.5p in the top tier.
Blue-chip banks were likewise enjoying further share gains after the Bank of England said it was "open for business" to boost finance for Britain's lenders.
Bank governor Mark Carney's remarks helped Lloyds Banking Group, Barclays and Royal Bank of Scotland make robust gains, following a solid previous session in the wake of encouraging third quarter figures from rival Santander. RBS lifted 3% or 11.9p to 368.4p, in light of Mr Carney's remarks, building on increases after Spanish-owned Santander said UK profits rose 28%, which sparked hopes for the raft of bank earnings figures next week.
Barclays followed with a 1.4p rise to 267.9p, while Lloyds added 0.2p to 80.4p after setting a new five-year high on Thursday.
Royal Mail's gains showed no signs of easing as an upbeat note from Panmure Gordon put a £5.7 billion valuation on the group as it predicted further rises to come.
The group rose 26p to 555p, 5% up in the day and nearly 70% higher than its 330p float price earlier this month as Business Secretary Vince Cable as he faces mounting criticism for setting the initial price too low.
The biggest FTSE-100 risers were RBS, ARM Holdings, up 22.5p to 983p, G4S and Tullow Oil, up 19.5p to 978.5p. The biggest fallers were International Airlines Group, down 14.3p to 349.7p, Hargreaves Lansdown, down 30p to 1155p, BSkyB, down 21.5p to 928.5p and Vedanta Resources, down 20p to 1068p.