It would be interesting to discover if this is in fact from wood-burners. Sounds more like industrial or rubbish burning but you could be right. Haringey, in keeping with other councils, does not have anyone tasked with investigating smoke pollution with regard to smokeless zones. Wood burners come in two kind-regular and those which burn at a temperature which supposedly neutralises the smoke effect. These are specified as such but how to detect which is which from the outside would be very difficult.
See the new discussion I just posted on air quality consultations organised by the council.
It's illegal to leave an engine idling for more than one minute. New campaigns kicking off about this, so you could warn them. It's a special skill displayed outside schools to keep the RangeRover warm while waiting for the sprogs.