John> Thanks very much indeed -- that has me sorted.  I'll give
    John> imshow a go as well when I get a chance.

    John> I've attached an image of the results to give you an idea
    John> what I'm up to.

Very nice..  what do the colors represent, pray tell? 
Nothing too exciting I'm afraid.   I've got this object I call an atlas which is a collection of maps.   Each map specifies the list of shapes (=countries/states/counties etc) that make up the particular map.

Anyway, to produce this picture I just numbered each country according to the order it appears in the list in my 'World' map.   This is just a toy I've been using for testing.

 Also, in case
you missed the announcement for 0.65, matplotlib now a number of new
colormaps, in addition to the trusty jet.

   autumn bone cool copper flag gray hot hsv jet pink prism spring
   summer winter
I did see that -- I'll have to see about making the colour map choice available to everyone (or maybe just check today's date and use spring, summer, autumn, winter as appropriate).

John