After blundering about for several days, attempting to find a solution to my mono-printing problem, I fell into what looks like a solution entirely by accident. Today, for the first time in several months, we were able to get to now of the local garden centres. In addition to the supplies for which we had actually gone there I noticed some rather good logs for the wood-burning stove, and bought a bag. When I got them home an idea suddenly struck me.
The logs were sold in coarse sacking. I emptied the sack and cut it up to give I piece of the right size. My experiments with printing, using it to provide the kind of texture for which I have been looking, have been quite successful so far. Entirely by accident, I might have solved my problem.