Food for thought indeed! I was just watching a Fairbanks Alaska pilot brief which mentioned the subject due to 26' of variation. So anything written down needs correcting to MAG.
To carry on with the thread, the wind that ATC gives these days ( At LON STN ) anyway, is an average reading for the last 7 mins, or was it 9 mins. Is this wind also MAG? I always ask for an instantaneous wind if it's looking grey or lumpy, so I assume that is MAG.