BOAC there is all manner of !!!!e out there for this one.
There is a requirement for the SAFA checks to have something on your Plog declaring your minima. If its not there its a finding.
As far as I can tell if the ATIS states to expect xxx approach but you get a visual before getting cleared for it you stick that minima in the box. If you go visual before any mention of what type of approach you are likely to do you still need to stick something in or they get thier knickers in a twist.
Personally I just make something up usually adding 500ft onto the airport elevation or just fill it out with some approach for that runway. But I can see that coming unstuck if the inspector wasn't a pilot and realising it was a load of rubbish just to keep the paperwork right.
Some folk stick VIZ in the minima box as well as the App box. Would work 90% of the time but I am sure the French would have an issue with it if you got SAFA checked.