Thanks for all the comments.
Lots of people still say "why do go to all that trouble when you can hardly see in the cab when its moving". True to some extent although on the open cabbed C Class the backhead is very visible. The fact is it IS very obvious when running even on a closed in cab like the Brit. For a start there is a driver and fireman sitting in natural and visible positions. And there are no big Brass valves filling the cab all too evident through the windows or levers sticking up in the air!.
Control (another thing people comment on) is not a problem. You simply remove the cab roof (on the run if necessary) make any adjustments, then pop the roof back on!
Driver's brake valve = axle pump by-pass valve
Driver's regulator = regulator
Driver's blower valve = lubricator steam boost
Manifold valve = blower valve
Fireman exhaust injector water valve = water gauge drain