I downloaded the map update to a USB stick and inserted this into the car slot. The satnav system asked about installing the update and I said yes, but it just stuck there for more than an hour. Is it actually doing anything? We eventually had to switch off the engine before it had finished. Does it lose all the processing it has already done and start from the beginning again?

It would be really nice if the software showed some sort of progress display as it is updating.

It will continue when you next start the car so long as you don't remove the USB.

Can take up to 1hour 40minutes depends on how big the update is.

Yup, I spent about 90 mins adding maps F10 recently, while trying to sort out another issue. Switch on your engine, switch off the auto engine stop, and either let it run, or go for a drive. You're right that some progress would be nice to see, but you just have to wait it out.

Thanks unofix, that's really useful to know. We seldom do journeys as long as 1 hour 40 minutes, and will do even fewer with petrol prices rocketing, so this update is going to have to stretch over more than one journey.

Unfortunately I removed the USB stick last time, so when we next use the car I'll leave it in when we stop the engine and hope for the best.

The update consists of many individual files of vastly different sizes. As the update progresses it loads each file, if the update gets interrupted by you switching off the car, then any partly updated file will be canceled. When you next start the car the update will begin again from the last complete file loaded.

So if my update contains 

C:\> unzip -lv .\Map_26177537498_Update.zip
Archive:  ./Map_26177537498_Update.zip
 Length   Method    Size  Cmpr    Date    Time   CRC-32   Name
--------  ------  ------- ---- ---------- ----- --------  ----
       0  Defl:N        2   0% 08/04/2025 04:40 00000000  DONTINDX.MSA
   24560  Defl:N    24570   0% 08/04/2025 04:40 65a69619  SyncMyRide\HB5T-14G386-TJB.tar.gz
    1703  Defl:N     1708  -0% 08/04/2025 04:40 b54015d4  SyncMyRide\JR3T-14G424-BK.tar.gz
16347849601  Defl:N 16313693716   0% 08/04/2025 04:40 b6876953  SyncMyRide\JR3T-14G421-BK.tar.gz
9083557966  Defl:N 8970705207   1% 08/04/2025 05:00 8aa4d789  SyncMyRide\JR3T-14G422-BJ.tar.gz
746055635  Defl:N 745395584   0% 08/04/2025 05:12 0c79fc16  SyncMyRide\JR3T-14G423-AB.tar.gz
   47243  Defl:N    47056   0% 08/04/2025 05:13 05ac4011  SyncMyRide\GB5T-14G386-AE.tar.gz
     790  Defl:N      291  63% 08/04/2025 05:13 a8845809  autoinstall.lst
--------          -------  ---                            -------
26177537498         26029868134   1%                            8 files

and I already can see in the Settings->SystemUpdate->Info that my maps moved from F10 -> F13 I have already passed/processed the biggest file in the update ?

Thanks 
Claus