Whitworth is a British standard, the original one in fact. Later to become BSW (british standard whitworth) it generally became the course thread option and BSF the fine. Roughly equivalent to your UNC and UNF respectively, indeed UNC and BSW threads will work with each other as pitch is usually the same. Whitworth used to normally have a larger bolt head size than BSF, thread size for size, but during WW2 it was reduced to match the narrower BSF bolt head size to save metal and simplify tooling, so any BS spanner (wrench) of particular thread diameter would fit either.
Most body and suspension fixings on Morgans have been for some time UNF, spanners and sockets for which are marked in AF (across flat) sizes, although I believe before that Morgan used BSF fixings. Full imperial socket sets cater for all three hex head standards, original Whitworth, BS and AF. As there is a spill over some BS sockets will also be marked with a smaller thread diameter Whitworth (W) as they share the same hex head size. This is equally true for imperial spanners.
Hope this doesn't leave you too confused
