Switched to US settings and it looks like it's having to reinstall 8.1 (Cortana's there though).
Do we know what else will change? Very tempted to do the same.
Edit: Can I also say so far this update is bloody awesome. Massively impressed so far with the keyboard, shortcuts, new animations...loving it.
My next phone after my Lumia 920 may be a Windows Phone again after all.