We're programmatically adding courses/activities/pages etc to moodle. We'd like to also add restrictions but I can't find the database table that deals with restrictions? could someone point me in the direction please?
You are in the wrong forum. For development questions, try the General developer forum.
With respect to your question, if by restrictions you refer to the Restrict access conditions, then these are availability plugins which are located under your-moodle-root/availability/condition. If you're not looking to add restriction types, but only to manipulate existing conditions in your programatically added instances, then the availability conditions are stored for each instance in the availability columns in the respective table. For course section it would be in the mdl_course_sections, for activities and resources it would be in the mdl_course_modules, etc.
hth
If you are using Moodle 2.7, the new conditional activities API should help:
https://docs.moodle.org/dev/Conditional_activities_API