In my opinion.I think it is all a case of terminology!! (so that they can charge you more)
Depending upon what mix I am am making up I use one of three products and they all come from the 'building section (not gardening section) of B&Q.
e.g.
Garden section = Silver sand = Kiln dried sand in Building section.
Grit sand in garden section = River/coarse sand in Building section.( for concreting not building)
Fine grit in garden section = Ballast in Building section.( this can be seived to give either grit only plus grit sand as previous item.
I had it out with a B&Q employee re what's the difference between the products in the garden section which cost about three times as much as similar products in the building section.
If you heard the waffle about salt content, pH etc you wouldn't believe it. I left him to his opinions and headed up to the building section 8)