I wonder, in a situation like this, is it even an option to turn some of those cancelled LHR flights into CDG/BRU flights to let people get at least close?
Although it's probably too complicated, and people generally want to land in the country they planned on, and may not think of such options....
Especially with UK outside Schengen zone, I think this is pretty complicated for the airlines to implement on a wide-scale.
But obviously it could be a good solution for proactive passengers with the appropriate passports.