My instructor just mentioned the fog lights in passing when going over all the controls for the first time, and didn't say anything about when it's foggy enough to use them or not. Though that was in the first lesson of so far just four and none of them were in fog or even more than a light drizzle so there may well be more to it.

With indicating, she said to always indicate when turning at junctions even if you don't see anyone as there could be someone round the corner you can't see yet. On the other hand, when first moving off one should only indicate if there is someone else, and that if the road is empty then to not indicate at all (and that the driving examiner will check if you're actually doing so or just always indicating). Roundabouts (which was today's lesson) get more complicated with indicating/not indicating depending on which exit you're taking, where the exit is, where the arrows on the road are pointing, and whether or not the road planner has done something silly with the roundabout.