The problem is not only with the power going down but starting up again. Have a look around for "black start"

This will get you going:
Wiki "black start"

P.S. Didcot 'A' is now decommissioned and Didcot 'B' had a disastrous fire last week and lost at least half of its capacity and its black start.

I understand there are only three Black Start power stations in the UK to kick off the whole grid. It is not a trivial exercise.