After you have changed the language, I would suggest you to update to the latest software version in the "About phone" menu then do a factory reset before starting to use it. (I've done the same)
Thanks rhen, my biggest prob was I didn't get the welcome screen when I turned the phone on, so no language change option. It came up when I tried again later, so all is good now
There was no welcome screen for me neither.
Seems like someone already turned on the phone. Maybe seller's QC tested the phone before sending it out.
But just to be sure I've made the factory reset after update.