Did you try creating a new addressbook, and then importing to just it? Thunderbird gives that option, but you must FIRST create the new, empty list.

The problem is that an "address book" and an "address list" are two different entities.

Yes you CAN create a list within an address book, and use the import function, but in stage 2 you are asked where you want to import to - and you're only given names of address books, not lists.

Which would be fine, but you can't use the name of an address book in the To: field when writing a message.

A possibility is to exit thunderbird and copy all abook* files from one profile to the other.

Where would I find the files in the profile please?

You can locate the profile this way: - click help>troubleshootinginformation - scroll down left side to 'profile folder' and click 'open folder' - exit thunderbird - you are now in the profile. If you list the entries alphabetically, there will be a number of entries beginning with abook. Those are the addressbooks. Copy to the other PC the same way.

Thanks, I've achieved partial success using this method.

There are still some address lists that haven't been picked up in this way, but I think I need to go back to my original system and do a bit of reorganising before trying again.