anyone coming at this for the first time, theres an infuriating failure in the process that is not mentioned anywhere.
the first time you go to get a map at landrover.here.com , a map download tool is downloaded...not a problem. When you go to get the map a second time, the downloader is opened, and tells you you need to download to a USB device.
Sticking in a new USB drive, it says it has to be formatted to FAT32 and asks you if you want to do it, but when you click yes, it just falls over. No problem, just right click on the USB stick and format it yourself....except windows 10 no longer supports formatting to FAT32, only exFat or NTFS.
Look up solutions online and folks tell you to do it via a command prompt. But then you find that's been crippled by windows 10 to only support USB drives up to 32GB, not big enough for the latest map download !
And the downloader won't allow you to download to you hard drive, so that you can figure this all out later !
Anyhow, the solution is to download a utility that can do it. In my case I used guiformat-x64.exe, this is a windows program that does allow you to format drives of any size to fat32. You can find it here
http://www.ridgecrop.demon.co.uk/index.htm?guiformat.htm . downloads at your own risk etc.
So whoever designed the map upgrading process, overlooked the fact that only supporting FAT32 on the USB drives, made it incompatible with the vast number of home PCs, once the download size passed 32GB.
Hope the above helps someone else coming at this for the first time with a windows10 system.
The actual download wasn't too bad, took about 1:40. However, given theres well over 700 files in the download, I'm guessing if they compressed, zipped, and then unzipped after download, it wold reduce the download time significantly.