Britool spanners had the A/F size as part of the spanner part number, which gave some strange numbers when it came to the Whitworth and BSF sizes.
Going back to the original question:
Whitworth was the first 'standard' thread as invented by the guy it is named after.
That series of thread sizes was used up until WWII when a need for some standardisation was introduced, so British Standard Whitworth or BSW was introduced, along with British Standard Fine, a fine thread as its name suggests.
As part of the rationalisation, the spanner sizes were combined so that BSW spanners also correctly fitted BSF bolts as well, but not always in identical sizes, they run a 1/16" out by memory.
So pre-WWII, heads sizes were larger on Whitworth bolts and nuts, and BSW is only used for WWII onwards fasteners.
When I started work in the early 1960's, I had mainly BSW/BSF stuff, but UNF and UNC were coming along quickly, so I added those as well to my toolbox. When I went to Sweden for factory training on Scania trucks in 1971, I had already started adding metric spanners as well. We had a system at the place I worked where you could buy tools and pay them off with so much a week out of your wages, which helped a lot when you were buying the larger spanners in Britool branded stuff.
Eventually I got out of mechanicking due to a bad back, not helped by manhandling damn great engines and gearboxes about! but kept all of my tools.
Most of the Discovery V8's are UNC, most of the injection system is Metric, I haven't come across any BSW or BSF yet.
BA sizes are another weird one, I bought a Britool 1/4" socket set for some ridiculous amount, and it had BA, Metric and A/F or Imperial sizes. Still got that today with most of it still there.
As mentioned earlier by welshlaner, there is a comprehensive set of tables on our websites:
http://www.stationary-engine.co.uk/Tables/Mech1.htm
http://www.oldengine.org/Members/Diesel/Tables/Mech1.htm
Peter