I've seen one picture of the interior, check-in desks. Would the North building have contained waiting areas and customs as well, or was that relegated to adjoining prefabs/Nissen huts/tents?
It baffles me slightly that Heathrow took so long to see any major improvements considering it was the first welcome to Britain for new travellers. But it's also charming in a way. Certainly would have given foreigners, like myself, a taste of the "make-do-and-mend" mentality that Britain is so famous for.