I'm increasingly thinking it'd be a good idea to split countries out from tags into their own vocabulary (drop-down form along with sectors) - probably make them children of the Regions tags.
This'd mean that we could make the regions views auto-generated - using taxonomy depth (don't ask) to make Western Europe "anything tagged in any country in western europe", and the western europe tag being for things at that level (world wars? Euro parliament stuff?), to save double-tagging.
More usefully, we'd be able to do things like google map views dropdowns by country and stuff like that, and have a countries-only tag cloud.
If people think this is a good idea, we'll need to find all the existing countries in the tags list along with their tag ids (easy in admin >> taxonomy manager) then it's a few database queries to change the vocabulary to 'regions'. Also if it's a drop-down we'll need to make tags manually for any countries we don't already have tags for - either on demand or as we set it up.
What do people think?