If I'm understanding you correctly, YatesJones, I believe I recently encountered a similar situation, so I'll tell you what I learned in case it will help.
We knew when and where both sets of my husband's great-grandparents died (in England) because I had purchased their death records.
I couldn't find an obit for any of them. I sent a query to the local library and they couldn't find any obits, either, so no clues for us there.
I sent a query to the local council and was informed that the g-grandparents weren't buried in any of their cemeteries. I assumed they would have the records for burials in the local churchyard cemeteries but that assumption turned out to be incorrect. (None of these burials are listed anywhere online.)
We reached out to the local church that was associated with my husband's family. Someone at the church checked their burial register, which is still located in the church (because it's not full yet), and found the burial information for all four of my husband's great-grandparents. (There were no tombstones, so inscriptions wouldn't have shown up if any local history society had done transcripts, but I don't think that has happened, anyway.)
We were told that churchyard cemeteries are private property and therefore not under the control of the local council. This particular church keeps their registers in the church until they are full and then they are sent to the local archives.
So, if I'm understanding your situation correctly, my advice to you is this: contact the local churches directly, provide as much specific info as possible on the deaths of the people in question, and ask them if they still have access to their burial registers for those dates; and, if they do, ask if they will do a look-up for you. If they don't, ask where the registers are currently being held and how you can request a look-up from that place.
Good luck in your search!
Regards,
Josephine
