Ask UK

If you've got wind problems (😏) then the 1 to 4 with aggregate slung in to add strength will do the trick.

I live in Scotland's countryside. Very, very windy at times. As in it's difficult to walk at times type of gusts, and the rain can spend the day going almost sidewards not downwards.
And one of our sheds is built off paving slabs. Now, admittedly, I didn't build and I probably wouldn't have built it like it is, but it's passed the test of time all the same.
What they did was:
Plonk the slabs down. B Shuttered the sides.
Concreted over slabs to tie it all in and give it lateral strength.
Built the building and screed it down, then built around the bottom of the shed a little bit to stop any sideways sliding motion in the wind.
Wouldn't pass any building regs but it's been up for decades and it's still here.

Edit: you could probably do the above slab way with external self leveling compound, not concrete. Flatten, slab, shutter, self level, wait, build greenhouse and screw it down, put something around the edges of greenhouse to stop it from going sideways.