You need to change/add keyboard layouts in the Language settings.
Just go to:
Start --> Settings --> Time & Language --> Region & Language
Then either:
- Delete the English language then go into Finnish and add the preferred English layout to the already existing Finnish one
- Go into the English tab and add the preferred English layout then delete the Finnish layout from the list
Either way you will be able to switch keyboard layout. In the first case maintaining the Finnish Region and Currency. In the second switching not only layout but Region and Currency as well.