Hello Guy,
Regarding your search for locating a possible burial place for your relatives, i can't help you directly but i can point you in the right direction.
I myself have been looking for burial sites previously for relatives in the Ton Pentre, Gelli,and Treorchy area, and have found the staff at Treorchy library very helpful indeed. They have the burial records for that area and can link them to a particular address, which should help you as the name you are researching is a difficult one in Davies. The contact i have is Gillian Thomas and the e-mail address is;
Gillian.thomas@rhondda-cynon-taff.gov.uk
Best Wishes
Tallpaul.