>     Not I, but allow me to recommend http://gmworldmap.com/ to anyone in the same position.

>     Maybe it's my computer. Or my internet connection. But the above loads incredibly slowly and
>     also the scale won't go below about 100 miles to the inch.

It may be your computer. It certainly chews up a ton of CPU when zooming in or out.
But it will zoom down to 100m/grid line. Of course, you can unilaterally declare
the scale to be anything you want.

Also, look at http://gokml.net/maps

This is Google Maps, but you can take all the text off the map (among other useful things).

Jonathan