Appreciate it's a US-bias, but can't find a way to stop the abbreviation of County, eg Essex becomes ESS.
What have I missed?
In Administer > Localization > Address Settings, you can change the mailing label format to use {contact.state_province_name}
instead of {contact.state_province}
.
It is not currently ready, but the localization (translation) system of CiviCRM does have support to define better defaults based on the locale. Work is being tracked in: https://lab.civicrm.org/development-team/translations/issues/1