I use an online contacts system to synchronize contacts. Google Contacts works fairly well, in conjunction with the gContactSync add-on in Thunderbird. This means that contacts are also available to my Android phone and tablet.

If you are averse to Google, then another approach might be to use an add-on which synchronizes address books to IMAP servers. This is useful between installations of Thunderbird, but no-where else that I know of.

https://addons.mozilla.org/en-US/thunderbird/addon/addressbooks-synchronizer/

Disclaimer: I haven't used this one for some time so don't know how well (or if) it works at present.

To do a one-time transfer of addresses, I'd export them from the old application to a CSV file and import this into Thunderbird's Address Book.

You will need to align the data fields in the CSV file to the available fields in Thunderbird's Address Book. The import tool in Thunderbird can help with this, but many users seem to prefer to massage the CSV file directly in a spreadsheet program.

http://kb.mozillazine.org/Import_address_list_from_text_file

Some advice on use of the import tool here: http://xenos-email-notes.simplesite.com/417788922

Thanks, sounds a bit long-winded but I'll give it a go. Quite happy using Google, although it seems very odd to me that contacts do not auto-sync when using the same account on Thunderbird on different devices.

Email doesn't include address books. Even in the Google world, Googlemail and Google Contacts are two separate applications, but they can be tied together via your so-called "Google Account".

Thanks for your help

Some folk also use this. I do not.

https://addons.mozilla.org/en-US/thunderbird/addon/addressbooks-synchronizer/?src=cb-dl-popular