* Banks, defensives extend recent losses
* Miners bolstered by iron ore deal
* Fourth-quarter GDP revised up to 0.4 percent
By David Brett
LONDON, March 30 (Reuters) - Britain's top share index was 0.1 percent lower by midday on Tuesday after banks handed back early gains, offsetting buoyant miners which were helped by a deal that could save billions of dollars in lost revenue.
At 1035 GMT, the FTSE 100 <
> index was 4.31 points lower at 5,706.35, below an earlier 21-month intra-day peak at 5,742.75, having closed 0.1 percent higher on Monday."Investors remained perplexed as to whether to build on equity positions or not as we head into the end of the quarter," said Nick Serff, market analyst at City Index.
Banks reversed early gains and extended the previous session's losses, with global heavyweight HSBC <HSBA.L>, down 0.6 percent, and Barclays <BARC.L> off 0.7 percent.
Part-nationalised banks Royal Bank of Scotland <RBS.L> and Lloyds Banking Group <LLOY.L> shed 2.3 and 1.8 percent respectively, unsettled by uncertainty about what a British government might do with its stakes in the two following the impending general election, expected on May 6.
Oil majors also reversed earlier gains as crude slipped to around $82 a barrel, with BP <BP.L>, BG Group <BG.L>, and Cairn Energy <CNE.L> 0.1-1.1 percent lower.
Drugmakers continued their recent downward trend, with Shire <SHP.L> off 1.6 percent, while GlaxoSmithKline <GSK.L> and AstraZeneca <AZN.L> each fell 0.8 percent.
Other defensive sectors such as drinks and tobaccos were also weak, with Diageo <DGE.L>, Imperial Tobacco <IMT.L> and British American Tobacco <BATS.L> down 0.2-0.5 percent.
MINERS HIGHER, JAPAN DEAL
Miners were boosted after BHP Billiton <BLT.L> and Brazil's Vale <VALE5.SA> said they had persuaded Japanese steel mills to buy iron ore based on a quarterly pricing system as of April 1.
The move signals the demise of fixed-price annual contracts analysts said were costing miners billions of dollars in lost revenue. [
]BHP Billiton shares added 1.1 percent, while Xstrata <XTA.L>, Rio Tinto <RIO.L>, Anglo American <AAL.L> and Antofagasta <ANTO.L> added 0.8-1.7 percent helped by a sector review from Deutsche Bank, which raised target prices.
Oil services company Amec <AMEC.L> added 2.9 percent after it acquired British consultancy Entec for an initial 61 million pounds, prompting Seymour Pierce to up its rating to 'outperform' from 'hold'. [
]Mobile telecoms heavyweight Vodafone <VOD.L> rose 0.6 percent following press reports concerning possible dividends from its U.S. wireless joint-venture with Verizon <VZ.N>.
There was better news for British-focused businesses as data showed the economy came out of an 18-month recession in the fourth quarter of last year with more momentum than expected. [
] (Editing by Dan Lalor)