* Within-day gas down 0.15 pence at 33.50 p/therm
* System oversupplied by 8 mcm
July 1 (Reuters) - British prompt gas prices inched down on Friday morning due to an oversupplied system amid thin trade.
Gas for instand delivery was down 0.15 pence at 33.50 pence per therm at 0829 GMT from the previous settlement, while the weekend contract was 0.05 pence lower at 33.40 pence per therm.
Demand was forecast to be 184 million cubic metres (mcm) on Friday while flows were expected to be almost 192 mcm, leaving the system oversupplied by 8 mcm, National Grid (LSE: NG.L - news) data showed.
Receipts of gas from the UK Continental Shelf are currently at 128 mcm/day compared to an average 123 mcm on Thursday.
The increase is mainly because the FLAGS pipeline, which which transports gas from fields in the North Sea, is back from maintenance.
Flows from St Fergus TOM and St Fergus Shell were higher on Friday. The InterconnectorUK has also returned from maintenance and is nominated for around 40 mcm of exports.
The contract for winter 2016 gas delivery was slightly higher at 43.10 pence per therm.
In the Netherlands, the August contract at the TTF hub was up by 0.04 euro at 14.27 euros per megawatt-hour.
In Europe's carbon market, the front-year EU allowance price was down 0.06 euro at 4.41 euros per tonne. (Reporting by Nina Chestney)