Thanks, I've tried exporting directly to the SD card. I end up with a folder called maps and a file called wwww.md5sum.txt.
A md5sum file should not be a text file. I suspect the Mac is converting the file type to .txt as it dislikes executable files but you can't execute this type of file on a mac, except maybe in Terminal.
I've been in touch with the Skoda technical people that can only tell me that it works on their Mac!