You can, of course, zoom and pan the map as you wish. Panning is most easily done by simply moving your cursor onto the map, holding down the left mouse button (on PCs), and "dragging" the map.
Clicking on the firm/base name on the right will also give you access to links which will display a zoomed-in aerial view for the base's location, either on live.com or google maps. live.com often provides a higher resolution view than google maps (though frequently older). Note that the live.com view, which comes from Microsoft, may only work on Macs if you use the Firefox web browser.
Asterisks on base names on the right indicate status - no asterisk means the location is accurate. Please report any inaccurate locations that you discover.
Many thanks to Graham Keens for finding the locations of the bases for the large multiple-base firms.