I tend to avoid using the drop down field for counties in the UK since - unlike States in the USA, or Departments in France, for example - there is no one true definition for them (is it London, Greater London, Islington, etc.).
Instead, I remove the county drop down and add another supplemental address line if required.
Although there are some forms on ...
It turns out that the "Search Primary Details Only" setting causes this problem (found under Administer-> Customize Data and Screens-> Search Preferences). It seems that if this setting is off, the listings and export will default to the address which was created earlier.
See here for details:
Contact Search Results Address Type
This is a weird behaviour ...
I began to import the database in pieces to a new installation to see if I could pinpoint where the issue might be coming up in the database. I found that the problem was with the civicm_setting table. There was a row added for address formatting that had the weird characters in it. I deleted the row and the problem disappeared.
The export issue is actually a confirmed bug, see https://lab.civicrm.org/dev/core/issues/464
I have had moderate success using hook_civicrm_export in a custom extension for a client where email location type is really important to their workflow.
Yes at the moment the list is manually maintained (see https://github.com/civicrm/civicrm-core/blob/5.15.2/xml/templates/civicrm_country.tpl#L172). You can file an update request at https://lab.civicrm.org/dev/core/issues
This seems to cover it: Edit 'existing locations' for events
"If you are wanting to do a one-off cleanup of obsolete addresses than as a UI work around you could edit the old events that contain those obsolete locations and set the first address line to DO NOT USE or NO LONGER IN USE or similar"
Thanks for the additional explanation! One approach you could try is to use Search Builder (Search > Search Builder) and search for contacts whose primary street address is null but whose street address of your default location type (e.g., Main or Home) is not null. If that doesn't yield the results you want, then you could search for your other location ...