Paul I felt a bit depressed when reading your first post, however I think it’s admirable that you are on such a worthwhile mission and after Neil’s comments (great!) I feel more optimistic.
Yes to use of polythene as mulch between occupants. No need then to dig or use poisons!
Around here the farmers give away large sheets of blck polythene which ere covering last year’s silage clamps. You may not have dairy farmers but keep an eye out for old plastic: if there are a few holes, just double up, or slip cardboard under a hole to keep light out.
Best of luck.
