FTSE gains; Petrofac firms, Prudential, BP fall

* FTSE 100 climbs 0.3 pct

* Petrofac lifted by Sharjah contract win

* Prudential dips following JPMorgan downgrade

* BP falls after RBS downgrade

By Tricia Wright

LONDON, Oct 11 (Reuters) - Britain's top share index rose at midday on Monday, led higher by Petrofac on the back of a contract win, while broker downgrades pressured Prudential and BP .

By 1107 GMT, the FTSE 100 <.FTSE> was up 14.54 points or 0.3 percent at 5,672.15. It closed 4.52 points or 0.1 percent lower on Friday at 5,657.61.

Petrofac was the top blue-chip riser, up 2.6 percent, after the oil and gas services company won a contract worth $250 million with the Government of Sharjah in the UAE.

The stock was also aided by a price target hike from Evolution Securities following a Syrian site visit.

Other broker comments were behind a number of individual equity moves, traders said.

Weir Group gained 2.3 percent after UBS upgraded its price target for the engineering firm to 1,700 pence from 1,400p, while repeating its "buy" rating on the stock.

UBS also raised its target price for sector peer Smiths Group to 1,550p from 1,400p, helping its shares to add 1.2 percent.

Inmarsat advanced 1.3 percent, recovering after falls last week when U.S. hedge fund firm Harbinger Capital Partners halved its stake in the satellite operator.

The stock was also given a lift by an upgrade from Goldman Sachs to "buy" from "neutral", with the broker hiking its target price to 940p from 875p.

BROKER DOWNGRADES

On the downside, Prudential shed 2 percent after JPMorgan Cazenove downgraded the insurer to "underweight" from "neutral", citing valuation grounds.

And BP slipped 0.9 percent, hurt by a downgrade from RBS to "hold" from "buy".

RBS said in a note: "For the share price to rise further, a higher proportion of investors must believe that BP was not grossly negligent in the Macondo disaster. This outcome is neither certain nor likely to be imminent."

BHP Billiton shed 0.4 percent. Rival prospective bidders may be looking to derail its $39 billion bid for Canada's Potash Corp , newspaper reports said, with China's Sinochem and a major Canadian pension fund among those working on plans.

U.S. stock index futures pointed to a slightly higher opening on Wall Street, helped by mounting expectations of further action from the Federal Reserve to support the economy.

"From the point of view of the equity market, (quantitative easing) would mean more stimulus ... and the markets might just read that as being good news for earnings or good news for growth," Mike Lenhoff, chief strategist at Brewin Dolphin, said.

Investors were awaiting U.S. corporate earnings, with figures due among others this week from Intel on Tuesday, JPMorgan Chase on Wednesday, Google on Thursday and General Electric on Friday.

Finance leaders meeting over the weekend in Washington produced no quick fix for global economic imbalances, suggesting the cheap money trade of selling dollars to buy emerging market assets and commodities looks set to continue for now. (Editing by David Holmes)