* Day-ahead gas prices fell 0.25 pence to 29.05 pence per therm by 0900 GMT.

* Within-day gas prices gained 0.35 pence to 29.15 p/therm. Work-day-next-week also rose slightly.

* The UK gas system is expected to be 12.3 million cubic metres (mcm) undersupplied, with demand predicted at 226.6 mcm and supply at 214.3 mcm, National Grid data showed.

* The undersupply comes as gas exports from Britain to Belgium are expected to more than double to 55 mcm/day on Monday due to planned seven-day maintenance at Belgium's Zeepipe, compared to Friday volumes.

* Due to the Zeepipe maintenance, more Norwegian gas is flowing towards the UK and then out via the Interconnector UK pipeline, a gas trader said.

* There is also a higher storage injection rate expected in Britain on Monday.

* Due to the reshuffle of flows, Norwegian flows to Britain rose by 30 mcm to 102 mcm/day on Monday from Friday volumes.

* Flows from UK gas production are 24 mcm higher compared to Friday on an increase via the Vesterled pipeline connecting the Heimdal field in the North Sea and the St. Fergus gas plant.

* Two nuclear reactors, Hinkley Point B-7 and Hartlepool 2, came back online over the weekend after unplanned outages, adding 1,065 megawatts of power capacity, EDF Energy data showed.

* However, wind generation is expected to drop on Tuesday, which could lead to more gas demand for power generation. Wind generation is forecast to fall to 4.3 gigawatts on Tuesday from Monday's 7.6 GW, Elexon data showed.

* Liquefied natural gas sendout remained low at around 12 mcm/day. Two Qatari cargoes are expected at the South Hook terminal this week.

* The UK July contract fell 0.40 p to 28.30 p/therm.

* The day-ahead gas price at the Dutch TTF hub edged down 0.07 euro to 11.20 euros per megawatt hour.

* Benchmark Dec-19 EU carbon contracts fell 0.14 euro to 24.91 euros per tonne.