So after a bit of advice
and quite a lot of emails back and forward from seed manufacturers. Today I laid down 324g over 9.2m² using a mix of three cultivars of Kentucky Bluegrass, or Smooth-stalked Meadow Grass if you are British.
At the moment I am only focusing on the upper level due to the fact that the fence work has taken an unexpectedly long time, so let's see how we get along.
Leveling the bed:
Seed on the ground: