Dave, as you say they’re not on Magic and if they were ancient a large three stone setting like that would surely be well known and documented, also there doesn’t appear to be any weathering on them especially when you compare them to the Hartwith Moor stone.
Maybe the local farmer is diversifying and is creating a megalithic visitors centre? Dunno mate.
Was there anybody at the timber yard to ask?

-Chris

All I can offer is thoughts/questions that will have undoubtedly occurred to yourself: i.e. They don't look old, but what the hell are they doing embedded in a wall like that? I can see the freestanding one as maybe a modern megalith, but why ones in the wall.

Somebody will know. Somewhere. Personally I suspect farmers put stones up like that just to confuse people like us.