Well, as promised I gave the 220 mag a preliminary run today.
Dug some old (and I'm talking 1990's) HP5 out of the freezer, it was an old roll from a pack that I use for testing, spacing, focus etc. I wasn't expecting anything flash given the age of the film, and non-importance of the trial I also tried a bit of equally old (perhaps 5 - 6 years) Rodinal that I had left.
Mixed it 1+100, and gave it 20 minutes, instead of the "suggested" 16, temp was +20º.
Film was exposed during the day in a variety of lighting conditions, in and around the garden, again, noting important.
Frame spacing looked OK, but not perfect. Spacing was a bit wider than I expected, and the last two shots were touching, just.
Base fog was "up there" as well with edge fogging too.
Worth a try if nothing else. And another shot perhaps with fresh film and developer.
Gary