I was getting this problem. On one of my accounts it appeared to be using the keyboard set to US English. No amount of changing settings to set it use the UK English keyboard layout worked. If I tried Windows Key + Space nothing happened happened - no selections appeared for choosing the desired keyboard. There was no language icon on the taskbar.
I added the UK English language pack and set the preferred language to UK English via Control Panel, Then via the Charms settings/PC Settings/Change PC Settings/Time and Language/Region and Language.
Selected 'Options' for UK English and Added the UK Extended Keyboard.
After that I could use Windows Key + Space to select the UK keyboard.
To be honest, I have no idea why that worked or which was the critical step. The other account on the PC did not of this problem. I assume I must have missed something when setting the new account.