Thank for your replies. Finally managed to update. Took over 3 hours to download from internet and about an hour to install.
Seriously worried about engine overheating during installation, electric fan cutting in constantly.
Surely Citroen could think of an easier way to do these updates.

Please advise how long it took to install map update via usb in car? I have a blue oblong constantly flashing across the screen and nothing else for last hour? Should it be taking this long?