Billy Madrid suggests that visibibility might be used as an indication of snow intensity. It seems to me that this would work well in the case of very dry (cold) snow in otherwise low humidity, i.e., an absence of mist over the snow field. Unfortunately, these conditions are almost unknown in the south of England. We just don't experience Canadian weather here.
It seems strange that the description of precipitation intensity on data for international operations should be relative to local norms, as Spitoon states, rather than a worldwide standard. Having grown up in the Tropics and worked long-haul, I do think that European Met forecasters tend to exaggerate precipitation probabilities and intensity, and suspect that some observers may also be guilty of it. Rather like my dear wife... Not helpful for young aviators when first abroad.