It would be very useful to show guests when selecting a booking time which time slots are already full. This would help as i believe that some guests find it confusing when the time they want doesn't appear, resulting in them phoning the hotel to ask if it is possible to book at that time when we would rather they can see a clear indication that there preferred time of 8pm say is full and to please select another booking time. I hope that makes sense.
At present we pull through the times that are available only and this does help to some extent in pushing customers to earlier 'Off peak' time slots. I can however see the issue where the customer will continue to phone you if they cannot find the time that they would like to book.
As there will be some customers who would prefer these times to not show then a compromise may need to be made or a toggle made available to you for unavailable/fully booked times to show in grey/strikethrough.
If there is any change to the current behaviour I will let you know.
Thanks for the feedback,