Ok, yesterday I swapped out the A/C relay for the Lighting relay as they have the same part number and the A/C worked normally but the running lights still don't work on low, first click, only the headlights in high and main beam. I'll check the fuses again but the problem was intermittent the last time they worked, which again, is why I really don't think it's the switch either, though next I'll check that for continuity before searching for shorts or bad grounds as they could be anywhere. I do remember driving through a deep roadside puddle which splashed up into the front wheel arches before the issue started so it may be a corroded terminal somewhere.