* Strike part of series of scheduled labour action
* Supply disruptions mitigated by stored crude
* No formal talks with Total currently planned -union (Recasts to say strike has started, adds details)
LONDON, July 30 (Reuters) - Workers at three of Total's TOTF.PA British offshore oil and gas platforms went ahead with a 12-hour strike on Monday, a spokesman for Unite said, with further industrial action planned if no agreement on new rotas is reached.
The strike by 45 workers at the Alwyn, Elgin and Dunbar platforms in the North Sea began at 1100 GMT. It followed a 24-hour stoppage at the same sites last Monday but stored crude cushioned against any immediate oil supply disruption. largest labour union Unite has also scheduled 24-hour stoppages on Aug. 6 and 20 and a 12-hour strike on Aug. 13 if it is unable agree new rotas with Total.
No formal talks with Total were currently planned, Unite said.
The three fields' oil production contributes about 45,000 to 50,000 barrels per day (bpd) to the Forties and Brent Blend crude streams.
Forties and Brent Blend are key oil grades used to set the dated Brent benchmark that prices more than half of the world's oil trades.
Meanwhile on a separate North Sea dispute, Unite said on Monday it would ballot offshore oil workers on whether to accept a new pay deal offered by Aker Solutions AKSOL.OL . is a heavy oilfield located 150 kilometres (93 miles) east of the Shetland Islands that is due to start production in the second half of 2018 with a target plateau output of 55,000 barrels per day.
A previous ballot voted in favour of a strike at Mariner and another British union, GMB, said last week its members on Mariner had also voted to stop work.
GMB had no immediate comment on Monday on Unite's announcement.