M12 x1.75 course thread size,seams to be the standard metric in the UK.
I don't I think have ever come across the Metric fine,and extra fine variations.
You go inside one of our hardware stores and ask for M12 bolt,your going get M12 x 1.75 course.
Sorry if caused confusion, got real soft spot for Whitteworth threads.
Joseph Whitteworth was the first person to standardise screw threads,and built a very fine rifle. In 1860, the British National Rifle Association held its first annual meeting at Wimbledon. Queen Victoria fired the first shot from a Whitworth rifle on a machine rest at 400 yards, and struck the bull's-eye 1-1/4 inch from its center.
So was Queen Victoria the world first bench rest shooter ?.