If you can't select a certain time slot that has been listed for you then this means that time slot is fully booked.
As I'm sure you can appreciate there is only a certain amount of space at your site and if that time slot has been fully booked out we can't make any additional bookings.
There are usually slots available at different times in the day
Another option available to you would be to bring a smaller vehicle if you have the option since there may be space for a van but not a HGV for example.
If you have any more questions around this please send us a message by clicking "Submit a Request"