This subject came up on another forum a couple of years ago.
When you think about it, it is a worthwhile service as some people cannot always get to a friend/relatives grave often. Especially if they live far away.
But some people were saying that there are businesses that do this work and have been doing it for years.
Sort of family business type operations that hand it down to sons & daughters to carry on etc.
I think the average price at that time was about a tenner per grave.