* FTSE 100 up 0.4 percent
* Index set for one of its best ever Christmas rallies
* Seen at 6,743 by year-end - Gekko Global Markets
* London market closes at 1230 GMT, reopens on Dec 27
By Francesco Canepa
LONDON, Dec 24 (Reuters) - Britain's top share index rose for a fifth session on Tuesday, putting it on course for one of its sharpest ever Christmas rallies, helped by a surge in broadcaster BSkyB.
Shares in BSkyB rose 2.1 percent, taking their gains so far this week to 4.3 percent, as a Daily Mail report revived speculation about a bid from Vodafone, aimed at bundling the groups' broadband, TV and landline offers.
The stock had traded nearly half of its full-day volume average for the past three months by 1140 GMT, compared to a paltry 10 percent for the FTSE.
London's stock market will close at 1230 GMT on Tuesday and remain shut for the following two days for the Christmas holiday.
The FTSE was up 24.37 points, or 0.4 percent, at 6,702.98 points in its fifth straight day of gains. The index has gained 3.3 percent in the past five days, its third-best run into Christmas since the index's launch in 1984.
After half of the FTSE's 10 best Christmas rallies the index fell in the first two weeks of January, Datastream data showed, making some investors cautious on the market's outlook.
"I'd be happy to let it go up until New Year. At the moment even if you wanted to (sell it) you can't do it (due to the low volumes)," said Andy Ash, head of sales at Monument Securities, said.
"Then if you're going to sell it on the seasonality there's plenty of volume on the first and second (trading days) of January."
Ash, however, said he would first take profit on the U.S. S&P 500, arguing that the FTSE 100 could still be boosted by money flows into Europe and a rebound in emerging markets.
The FTSE, which generates a quarter of its revenues from emerging markets, has risen 13 percent this year, less than half the rise in the S&P as the U.S. economy improved and the dollar strengthened, causing volatility in emerging market currencies.
Jordan Hiscott, senior trader at Gekko Global Markets, reckons the FTSE will eke out further gains this year, though could struggle to overcome 6,743.
Resistance could come into play at this level, he said, and the 14-day relative strength index (RSI), a momentum indicator, is moving back up towards overbought territory.