OK I've got my phone straight now... the only way I could do this was as follows....
1. Export all contacts in the phone to the SD card using ExportContacts.
2. Switch off auto updates on the phone.
3. Transfer the phone CSV file to the PC then import the contacts into googlemail.
4. Use googlemail de-duplication features to tidy up the list.
5. Export the tidy list of googlemail contacts to a CSV file.
6. Switch on auto updates on the phone, then delete all contacts from the phone.
(this took ages as I kept "exceeding the maximum number of deletes") The auto update also deleted all the contacts in googlemail.
7. Once both the phone and googlemail were devoid of contacts...
8. Import the tidy CSV file back into googlemail.
9. Auto update then drags all the contacts down to the phone.
10. Enjoy hassle-free contact synchronisation!
Thanks very much to everyone for their contributions to this thread!
