Les,
your advice is - as ever - both welcome and appreciated. And I do have a few grammes of benzotriazole put away for just that particular use. But my current printing problem is that I have a few negatives which I "experimented" a bit too heavily with: They're developed in monobath. The contrast is not only astounding, it's beyond what I thought was possible from FP4+... But referring to my notes, I am now going to try printing them on pre-flashed TT Baryte Vario, which of all my great hoard of paper has the most steps from mid-grey to white. If all else fails I'll sepia-tone the lot