bttt for more advice as i've never done this before and don't really know what i'm doing

how much MOT do i need for that area / volume when compacted down?

the hole has an area of 11 square metres (118 square feet), and with a compacted depth of 100mm (4 inches), that's a volume of 1.1 cubic metres (39 cubic feet)

i want to order it in today and get the compactor over the weekend to fill it in.

also, mortar to go on top of the compacted base and fix the slabs. 4 to 1 mix of sharp sand to cement yes? again, how much of the stuff will i need for a hole that big? will be doing about 25mm deep of mortar

thanks for any advice.