Address autofill is only enabled for U.S. English builds of Firefox, accordingly to: [[Automatically fill in your address on web forms]]. There is a way to override that, but Firefox may enforce rules that aren't appropriate for other countries/languages. Want to try it anyway? Here's how: (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button accepting the risk. ''More info on about:config:'' [[Configuration Editor for Firefox]]. ''The moderators would like us to remind you that changes made through this back door aren't fully supported and aren't guaranteed to continue working in the future. Since we have had this setting for a long time and I use it myself, I feel comfortable mentioning it.'' (2) In the search box in the page, type or paste '''formautofill.addresses''' and pause while the list is filtered ''Firefox should show about six preferences.'' (3) Double-click the '''extensions.formautofill.addresses.supported''' preference to display an editing field, and change the value from '''detect''' to '''on''' then press Enter or click the blue check mark button to save the change. (4) I don't know whether it is strictly necessary, but I suggest one more change: double-click the '''extensions.formautofill.addresses.supportedCountries''' preference to display an editing field, and add your two-letter country code. For example, if you are physically located in the UK: if the preference is blank, just list GB, and if it has "US,CA" already, add a comma and then GB (without an extra space). Then press Enter or click the blue check mark button to save the change. Similarly for AU, etc. Success?

No sucess, sadly. What a shame really, it's such a basic QoL feature, it's disapointing. Thanks for the help!