The 1938 and 1948 editions of the six-inch have the National Grid squares on the face of the map.
All editions of the six-inch have latitude and longitude printed in the margins.
On the Charles Close Society website, the modern 1:50,000 and 1:10,000 have a cursor that simulataneously displays the NGR to 1m and latitude and longitude to 8 decimals of a degree.
I tend to flip between editions and websites to obtain coordinates.