In the IGI (www.familysearch.com) under Robert Mogridge number 90 you'll find the marriage on 27 June 1765 at St Pauls Covent Garden. The possible christening may be Robert Mogridage number 22 on 17 December 1739 at Shobrooke, Devon. This is in the heart of the Mogridge country near Exeter. However, the IGI does not have all records (especially Wiltshire) and people often change names - so this may not be what you are looking for. But there aren't all that many Robert Mogridges around that date.