To illustrate how big of a deal this movie was at the time, there was a live-from-London television special one evening celebrating its premiere. German television network ARD or ZDF (I can't remember which) picked up the live feed: There were searchlights and men dressed in vintage uniforms manning an ack-ack gun placement. I could hardly wait to see the movie.
Unfortunately, producing-studio and distributor United Artists lost a lot of money on Battle of Britain. The film did not 'travel' much outside of Europe (read: the USA), which it had to do in order to make back the investment. As a tie-in documentary hosted by actor Michael Caine outlined most effectively, regular folk, including those on the Isles, could tell you next to nothing about the battle. And this was less than thirty years after the events. The idea of an ignorance of one's own history as being an 'American' thing is a false one. (Author Clive Cussler recounts a sobering personal experience in his non-fiction book, The Sea Hunters, where he was taken aback by some of his fellow Americans -- politicians in this case -- not knowing, or, more importantly, not even caring about their own history.)
Director Guy Hamilton, guiding light of Battle of Britain, claimed that United Artists lost ten million dollars (late 1960s currency) on the deal.
As a child what I liked was Battle's spectacle: The wide-screen; the colour; the music; the you-are-there vibe.
The now-defunct "Festival Theatres" repertory chain here in Toronto would screen the film every few years, and I would be there with interested friends.
As I've told people over the years, "Battle of Britain was my Star Wars."