UK GAS-Prompt prices slip on mild weather, high wind power output

* Temperatures higher than earlier in the week

* Peak wind power output to hit 5 GW

LONDON, March 9 (Reuters) - British spot gas prices fell on Wednesday as mild weather and forecasts for high wind power output curbed demand.

Gas for instant delivery fell 0.20 pence per therm to 30.30 p/therm by 0946 GMT, while the day-ahead contract fell 0.33 pence to 29.85 p/therm.

Britain's gas network was balanced on Wednesday with forecast supply of 313.1 million cubic metres(mcm) close to forecast demand of 313.5 mcm, National Grid (LSE: NG.L - news) data showed.

"The weather's a bit milder so that will knock demand at the front end," a gas trader said.

Britain's Met Office predicted temperatures as high as 10 degrees Celsius on Wednesday, a few degrees milder than earlier in the week.

"The latest (UK) weather runs predict... warmer than average levels from Wednesday onward, before cooling again from 15 March," analysts at Energy Aspects said in a research note published on Tuesday.

Peak wind power output is expected to reach over 5 gigawatts (GW) on Wednesday, National Grid data showed, up from below 3 (GW) on Tuesday.

There was ample supply and imports from the Netherlands from the BBL pipeline increased to around 28 mcm from levels below 25 on Tuesday.

Imports from Norway through the Langeled pipeline were near full capacity close to 70 mcm/day.

Further along the curve, the UK winter 2016 gas contract was unchanged at 33.40 p/therm.

In the Dutch gas market, day-ahead prices at the TTF hub inched up by 0.05 euro to 12.40 euros per megawatt-hour.

Brent crude futures traded above $40/ barrel on Wednesday, up more than 1 percent on Tuesday's close.

In the European carbon market, front-year allowances edged down 0.03 euros to 5.00 euros a tonne. (Reporting by Simon Falush and Susanna Twidale)