Thanks for the comments chaps.
The earth banks are formed from the dried bases you can by for putting flowers into. They do two kinds, the wet stuff just crumbles and is no good but the dried is quite rigid. I glue them to an mdf board and then cover them in a single layer of mod-roc (plaster impregnated bandage).
Then its just the usual pva/sand coat, sprayed earth tones and the hedges are glued on , madef from rubberised horsehair, again sprayed brown and then coated in pva and leaf/flock materials scattered over them.
You could form the banks using insulation foam (pink/blue) foam instead.