How do I see who I've invited?

In Booking centre your invites show in dark blue. Click the invite button on one of your invites and a window will show you all details for this invite.

This includes the events that you are including in the invite. For example it'll show whether you are inviting your opponents in a box league. For each event you can get a list of people who will actually see your invite by clicking on the number that appears to the right of the event. This number represents the number of people who could accept your invite. Clicking on it will reveal their names.