As a Brit, I'd never heard of Flag Day, and had no idea you guys had such a thing.
But then, the British don't make a big deal out of our flag these days as Americans do (Unless we're getting irked by the Far Right's tendency to try and co-opt it, but since we're generally agreed the BNP are a bunch of tossers it's sort of a moot point),
And we certainly don't have a Code of the Flag like you guys do. (I hasten to add I'm not saying that's better or worse, just noting that it's a major difference in our outlook). We're a bit more casual about it certainly.