My phone is now synching! Many thanks.
The problem seems to have been the permissions as you thought. However, when I tried to Ctrl-click on the BTConduit.bundle there was no "Show Package Contents" element. I had already gone straight to the plist section and updated the permissions there, but that didn't work. Thinking logically, I wondered whether there was a tree of permissions, so I changed permissions in the BTConduit.bundle and the Contents list as well, and now, at last, I have a full address book on my computer.
You are a star, Jools. Many thanks.
Mike