Here in the Netherlands, we prefer the word "England" (Engeland) to "Great Britain" (Groot-Brittannië). We don't even have a word for just "Britain". (Presumably it's Brittannië, but so far I've only heard the adjective "British" - Brits.) It seems perfectly natural to us that the part stands for the whole, and so I must have accidentally insulted quite an amount of Welsh people by calling them "English" as a kid. The fact that it's so logical to us is probably because 1. The language is called "English", and 2. There's still a large number of children's songs and rhymes about "England", and zero about "Great Britain". I remember learning in elementary school that the country to our left was simply called England, and didn't learn about any other name for it until I was at least ten years old.
Stephen Fry mentioned this on QI, and his guests seemed to be genuinely shocked that people could refer to the entire country by its part. As it turns out, the switch only took place halfway through the 20th century (not the name "Great Britain", but it being the only correct word), and not all countries/languages have adopted the new politically correct version yet.
My question is: in your country and language, does "England" sound like an acceptable alternative to "Great Britain"? Would you use the word for the country in casual conversation? In formal conversation? And which name were you taught in school?