Everyone should be assembled in the building 5-10 minutes before the time of your marriage.
It is essential that you keep to the time arranged for your marriage. If the start of your marriage is delayed for any reason the Superintendent Registrar may have to curtail your ceremony, leaving out certain elements; such as readings, extra vows and musical items. It is also possible that the marriage may have to be postponed, or at worst rescheduled for another day. This may require new Notices of Marriage being given and the payment of all fees again.
You should ensure that you and your guests have ample time to arrive at the venue. It is a good idea to check the local travel news on the day to make allowances for roadworks etc