Yeah but Greenwich is a place known world-wide, and I guess a high percentage of people mispronounce it (I was one of them).
It's known worldwide, but many people never heard an actual Britt pronouncing it.
In my country, it was always pronounced as green-each. Only in this thread I realised it's written Green-wich and pronounced gren-each.
And I'm pretty sure I'll forget it quickly and just keep calling it green-each.