Removed fake grass: next steps?

We've recently pulled up the artificial grass in the front garden of our new house (Wales) and are hoping to get some biodiversity back with some real grass, hedging and bushes, maybe some flowers.

First on the agenda is the grass. Underneath the artificial grass is a thick layer of damp sand, and beneath the sand is some kind of plastic/fabric membrane (pictured, with a hole in it). Underneath that is wet gravel, mud, random bits of concrete, etc.

My question is, can I just get some soil/compost (which would be better?), churn it in with the sand and put grass seed down? Or should I put the soil/compost on top of the sand with no mixing? And should the membrane come out? FWIW it we had quite a few weedies coming through the fake grass, so life was finding a way.

Massive thanks in advance for any insight!