Ian:
ASTM has a new training course on CD for commercial real estate that you might want to check out (You can get a free demo disk.) Go to ASTM.org and look under Training Courses, then go to the bottom of the page and click on the ESA CD link. That gives you a phone number to order the demo disk.
The disk will take you through a lesson then propt you with questions. It seems OK for someone starting out with Phase I's.