OK - 2 weeks down the line from the procedure to finally sort my knee out, and I went to see Justine for a bit of Physio-derived ear-bashing.
She was on great form today, but more importantly was very pleased with the progress that my knee is making.
She did a little bit of work on the medial wound site which has been a bit tender, and otherwise just told me to keep working on my strength and flexibility stuff.
I asked about the ACL, and she said that the best thing I could do was keep my legs muscles strong, because THEY are the support structure, and that the ACL had probably been like that for years.
She has told me to get back out on the bike and start building up my endurance again, although not to do any hard-core sessions for at least another couple of weeks. A little more probing from me and I was able to tie her down to what she meant.
She's happy with longer easy effort rides and to just keep an eye for any reaction, and adjust things accordingly. And I can gently up the effort level if things are OK over the next week.
NO eyeballs out hill sessions or leg-busters for now.
And absolutely no activities that introduce dynamic twisting - so running (as I expected) is out for the moment.
Better put my bikes outdoor clothes back on then.
This is great news!