BernardL and Harvey - Many thanks for your comments.
I'm not too disappointed with the end results, as such, just the lack of control. My disappointment is the fact that I have no idea how the end results happened. The film was, to the best of my knowledge, a fresh roll of PanF and it was exposed correctly. What I wanted was a negative I could work with. What I got back was something that's "interesting" in its own way but not remotely what I'd set out to achieve. Consequently, I have no idea how to recreate this effect - even if I wanted to.