So having failed to get the maps onto the Zumo, I deleted everything and started again.
Used Express to load the maps and lit loaded Northwest Europe successfully.
So how do I now get the remainder of Europe onto the device. I have a 4GB SD card which is enough. I've tried several times to load the whole lot using mapinstall. This appears to work for a while, but there is eventually always a communication error and the process stops.
Any ideas before I junk it?