A course booking is checked against every day of the course

Every booking for a course now checks for room on every day of the course, and an online one is charged the course price, however the booking reaches us. Your booking page already did this; now nothing can skip it.

No overfilled course days — a course booking that would overfill any day of the course is refused with “Course day is full”, whichever day it names
The course price, always — an online course booking is charged the course price, never a single day's