BSF (British Standard Fine) was made obsolete just after WWII, so I don't think that should concern you. UNF & UNC are the standard imperial threads that you will come across. UNF (United Fine) is a fine thread usually used when a nut and bolt are required and UNC (United Coarse) is a coarse thread usually used when a component is bolted into a tapped hole.UNC will normally take a higher torque.
Incidentally UNC and the older Whitworth are interchangeable up to under 1/2" (3/16" - 7/16") qafter which they aren't.
3/16" UNF is the same as 3/16" BSF and 2BA.
(If I'm not here, I'm either in my new workshop or on the golf course!)