Thanks again. First, as this has morphed into an update problem, no longer anything to do with my location, do you wish to move the latter part of this thread to another heading?
To answer your question, it shows free space on the device as 6243MB (there is no memory card installed). Therein, I believe, is a clue. The MyDrive screen shows that the Europe & UK map (the only one I have installed) (a) is corrupted and (b) is 6740MB. It gave me the option of omitting Russia (only TomTom could ever imagine that Russia is within Europe), which I did. The MyDrive home screen shows that my device is up to date, but the Go screen says "Update Failed". I just repeated the download procedure, same result. Maybe that's where the glitch is, it's looking for more space than it needs, or the removal of Russia does not take it below the max memory available.
I seem to have two options; 1, go buy a 8GB MicroSDHC card, which should remove the capacity problem - I will do that tomorrow. 2, MyDrive offers a further option, to load the maps without 3D buildings. I will try that tonight and let you know the result.