how do you book a registrar for a wedding??

me and my fiance are wanting to get married at Hardwick Hall, Sedgefield, which are licenced for civil ceremonies providing you can book your own registrar. does anyone out there know how to do this?? im really confuddled!! cheers

Yes, I made the mistake of booking everything apart from the registrar, so there’s none available for the time of my wedding. Apart from moving the time of the civil ceremony is there anything else I can do?