I've been to the National Library at Aberystwyth and checked out the parish records. There is an entry in the Llangunnor record of William Richard, carpenter/Mary Griffith marriage dated as you said. However there is then a succesion of baptisms to William and Mary Richards when we know they were living either in Llansawel or Talley. The baptisms clearly are not our William Richards. Even more disconcerting is the fact that I could not find any other reference to any William Richards/Mary marriages in Llangunnor
Also Talley record shows David son of Benjamin Richards, saddler, Melinwaun and Elizabeth Thomas, servant at Edwinsford
Nigel
best wishes
Nigel