You are able to cancel a booking from your dashboard.
Go to "List of Bookings" on your left hand sidebar:
You can view all your bookings here by selecting the date range you'd like to view.
You can also search for a booking by booking reference, event name, vehicle plate etc.
Once you've found the booking you'd like to cancel select it and the option to cancel that booking will be there in a green box.
You will receive an email notification of this cancellation.
Please note that this process is not reversible. Once a booking has been cancelled you can't restore it and the time slot is opened up for new bookings.