Sounds familiar , never known Japanese though , it sometimes reverts to USA English. First open word and do shift on the ' key …….. did it type @ symbol.
If not go to language settings to see if it is still set to uk English , if not you can re-download the language pack.
For browser problems go to region setting and make sure it is still on uk English
As a quick browser check type amazon in search box , not from a short cut , if browsers set correctly the prices should come up in ££££ not $$$$$
After making changes to language and region you must do a restart.
NOTE..... the culprit for the changes you describe is usually a windows creator update.