Hi Anne
St Marys at Cleator don't have many old graves left. I was up there a few months ago with my mother-in-law, who could remember visiting her grandmother's grave just by the church, but it wasn't there. We visited the priest's house, who told us the map/plan of the graveyard had been destroyed in a fire a few years earlier, so they have no record of who is buried there, and whereabouts. He also said that some of the graves are under the wide tarmac path that goes around the side of it. There is also a newish porch on the side of the church. I wouldn't be surprised if there are also graves underneath there.
So your relations could be there, under the path, like ours. Also if they didn't have much money at the time, they may just have had a wooden cross, which could have rotted away with time. I was really upset that they were allowed to do that with the path, how dare they?
Good luck with St Beghs.
Best wishes
Rosemary