witzend, I love that description about how the worms came in, it is very heartening. Last house my farmer neighbour used to grow the same winter wheat year after year and he said that the agronomist told him that his soil was barren, so he put nasty bulk fertilisers on it and he sprayed against insects with a big machine and the land remained barren and people locally developed some nasty illnesses, all in the same valley, near those fields
I did what I could on my allotment, discovered bocking 14 comfrey and never looked back, bees loved it and I always left some flowers for them. Our allotments, like oases in a desert of surrounding farmland, much now owned by men in suits. When I came here, I made sure to bring some bits of comfrey and they took hold and the bumble bees came and have stayed