BP lifts Britain's FTSE towards 4-1/2 month high

* FTSE 100 up 1.1 pct, at highest level since Sept

* BP gains after profit beats expectations

* Weir Group rises as oil price recovers

* Aberdeen Asset Mgt falls as funds under management shrink

By Alistair Smout

LONDON, Feb 3 (Reuters) - Britain's top share index rose towards a 4-1/2 month high on Tuesday, boosted by energy stocks as BP's results beat earnings expectations.

The blue-chip FTSE 100 index was up 1.1 percent at 6,859.47 points going into the end of the trading session, near its highest level since September 2014.

Oil major BP gained 2.8 percent after it beat quarterly profit expectations despite taking a $3.6 billion impairment charge in the face of low oil prices.

"On a standalone basis BP represents good value and with these numbers, we expect buying to come back into not only the sector but BP today," said Atif Latif, director of trading at Guardian Stockbrokers.

Oil company Afren (LSE: AFR.L - news) , which is in the FTSE 250 mid-cap index rather than the blue-chip FTSE 100, advanced 17.5 percent on prospects of a deal with Nigerian peer Seplat .

Weir Group, which makes valves and pumps for the energy sector, also progressed by 8.1 percent as the price of oil rallied on Tuesday, extending a rebound after falling to near six-year lows last month.

However, not all energy companies fared well.

Shares (Berlin: DI6.BE - news) in BG Group (LSE: BG.L - news) edged down after BG wrote $6 billion off the value of its oil and gas business in the fourth quarter.

Another underperformer was Aberdeen Asset Management (Other OTC: ABDNF - news) , which fell 3.5 percent after reporting a small drop in funds under management in the December quarter. (Additional reporting by Sudip Kar-Gupta; Editing by Gareth Jones)