iPhone stuck "Removing iCloud Data..." after iCloud sign out
After an hour I decided there was something clearly wrong, so this is what I did to resolve it:


Powered down (long press on the top button, slide to power off),
Powered up and entered password,
Opened Settings (I appeared to still be still logged in to iCloud, but iCloud was off - it seems that things were just half completed in the original sign out),
Signed Out of iCloud again (this time it finished almost immediately).


The In-App-Purchase test then worked fine.