UK GAS-Prices sink as crude oil rout drags on commodities

* Oil price plunge weighs on British gas prices

* Prices decline across coal, power and carbon

* UK gas system oversupplied by 22 mcm

* Temperatures above normal (Recasts with sharper gas losses caused by plunging oil price, broadens to include impact on other commodities)

LONDON/MILAN, Nov 27 (Reuters) - British forward natural gas prices sank on Thursday, extending declines across European commodities led by power, carbon, coal and most of all crude oil as OPEC's decision not to cut supply sapped energy markets.

Benchmark UK summer gas prices fell nearly a penny to 53.77 pence per therm, reversing earlier gains, after the OPEC oil exporter group said it would not cut output to arrest a slide in Brent crude oil prices.

Forward gas contracts, due to a long-standing practice which fixes long-term gas prices to crude, are sensitive to swings in oil markets. Oil at one point on Thursday fell more than $6 to $71.25 a barrel.

Spot gas prices dropped 3.5 percent to 57.15 pence per therm, taking their cue from the wider commodity selloff as well as milder weather reducing demand for gas-fired heating.

Prices for next-day delivery fell to 57.15 pence per therm by 1831 GMT, down 1.85 pence from the previous settlement, wiping away gains made earlier in the week.

At Europe's most liquid continental gas hub, the TTF in the Netherlands, day-ahead prices fell 2.15 percent to 24.15 euros per megawatt hour.

In Europe's carbon market, benchmark EU Allowances (EUA) were down 0.12 euro at 7.17 euros per tonne.

European coal futures prices for 2015 coal were down 35 cents at $72.75 a tonne.

The UK gas system was 22 million cubic metres oversupplied. Flows were expected to be 287 mcm/day, while demand was 265 mcm, National Grid (LSE: NG.L - news) data showed this morning.

An outage at Britain's SAGE natural gas processing terminal has ended, ConocoPhillips (NYSE: COP - news) said.

Gas flows from Norway's Langeled pipeline remained near capacity at 70 mcm, while flows from the UK Continental Shelf (UKCS) and the Netherlands via the BBL pipeline were higher than on Wednesday. (Reporting by Oleg Vukmanovic and Sarah McFarlane, editing by Keiron Henderson)