Still no joy from your friend Dalecosp but thanks for the tip anyway.
In answer to my own question I'm now using Japanese DW4 with Japanese OS X. And it's working fine, just need another computer with DW running at the same time so I know where I am with the menus.
I have another question though. Has anyone needed to insert double-byte characters into a database. We use phpwebhosting at the moment and they've told me that they don't plan to allow people to do this yet. Does anyone know of any decent hosting companies that have provided both this service as well as not having a server that is constantly crashing.
Cheers for any tips.