>I use "GivenName FamilyName" when speaking English and "FamilyName GivenName" when speaking Japanese. I assumed this was the default.

I only notice this in Japanese Anime and Movie DUP and I thought it was very strange. In writing in English, GivenName : FamilyName makes sense because that is how all English speaking countries work, but when you speaks it in that order, it all went off.

In Hong Kong most people have a Christian / English name so it isn't much of a problem. Although this tradition will likely erode away for obvious reasons.