> I assumed the route numbers are more of an American thing (although your comment seems to imply perhaps not)?

In my area (Connecticut), it depends. Some streets are known by their route numbers, vs some streets have route numbers and most people aren't aware of them at all. It's more common to refer by route number if it's a busy main road that changes name from town to town that it passes through.

Then there's upstate New York, with plenty of streets that are only route numbers, despite being otherwise residential normal roads.