If you're trying to access the temporary URL (i.e. example-co-uk.staging.com) you may get an ERR_SSL_UNRECOGNIZED-NAME-ALERT error.
This will be because the temporary URL can't load over SSL (via https://). To allow the temporary URL to resolve you'll need to ensure it loads over http://.
You may need to try an incognito browser tab after making any corrections to ensure https:// is not cached in your browser.