The Garmin mapping is fixed.
Format your USB stick as above and follow the above procedure.
Garmin Express will not identify the new update and will tell you you are up to date :
Ignore this and on the next screen opt to Reinstall Maps :
When you do, the download is very quick as it seems they only need to download one tiny section if you still have the previous files download on your PC.
This means it goes almost instantly into Installing Maps at 0%.
Once it gets to 50% it finishes and you can again follow the above procedure to reload the car mapping.