Hi A,
The best way to rid yourself of the nettles is to dig them out. You could also cover with Cardboard with a layer (4″ should do the trick) of compost on top of that. You may even then get an odd shoot appearing but they will be easy to remove/eradicate.
What is the drainage like on the area your thinking of cultivating. I think that may be your biggest problem? Not insurmountable but a problem perhaps.
Don.