WordPress Core, plugins, themes, mobile apps, and other strings can be translated from US English (
en_US) to British English (
en_GB), at https://translate.wordpress.org/locale/en-gb.
A lot of the strings will be exactly the same. Others will only change on spelling or the occasional different word. Capitalisation and word form (i.e. ending in -ed or -s) should be maintained or adapted as necessary.
You can find a detailed list of agreed changes for all English variations on this spreadsheet:
WordPress.org Shared English Variants Translation Glossary.
Note that some strings have been validated before these variations were decided, so if you see a different version, please submit a new string. If we ever get global searching across all projects, we’ll handle it then.
Other changes would be where demo content uses dollars and a US city that could be changed to pounds and London respectively.