Not much white stuff at LHR, only last night. We had a moderate wet snow covering. One runway was shut for half an hour for de-icing and braking action testing.
Most shorthaul never left origins. Long haul would use their enroute diversions, not worth risking coming into EGTT with so much disruption around the region. Wait it out somewhere with tech support, good facilities and transit facilities that can handle so many passengers probably without visa's....
BA long hauls would probably slip into LHR un-noticed as would VS. (Excuse the pun) Shellsuit south terminal (what is it called now BAA have given up LGW...?) are mostly non-ops such as FR/EZ and others would not operate from local airports.