Google maps indicte Church End was a couple of houses up from the church, about half way between Church Lane and Smithy Lane on the same side of the road as the church. But google maps often get locations a bit wrong.
Are you near enough to visit Friskney? If so, I'll bet one of the old locals or someone from the church will be able to point you in the right direction.
There look to be a few new houses and some warehouses in the village, but you should get a good idea of how it would have been when your ancestors lived there. Good luck.
