If anyone has a Zumo 660 running the latest 4.8 software, could you check to see if in page 2 of tools there is an icon for "Language Guide". Mine is missing.
Found the answer, Garmin dropped the Language Guide from firmware 4.80 onwards. So if you need it, just put the 4.70 GCD file back on again.
Studied the firmware 4.80 & 4.90 updates and found nothing that I had issues with, so I tried it out myself and it works OK.