...Prospects can book one (or more, if allowed) of the time slots - and there is a warning if they try to book 2 overlapping time slots
(e.g. to meet with 2 different sales persons at the same time). A prospect may also cancel his/her bookings.
Your sales persons may define different templates for the notification e-mails (invitation, booking confirmation, cancellation confirmation),
but only one template for each of the 3 types may be active at a time.