St Erth is a box with that configuration of toilet, IIRC, but you need to turn the light on there to see what you're doing, so I don't think there is a glazed section.... Other boxes seem to have the toilet in a different position, such as on the back wall, where there is a window, eg. Roskear, Par and Lostwithiel.
Liskeard has no window, but the toilet is at the opposite end from the entrance (internal) stairwell. St Blazey has no window (again you have to turn the light on!). Truro and Goonbarrow have downstairs toilets that you have to access by going outside and down the external stairs.
That concludes (for the moment) the Lavatorial Tour of West Country signalboxes!.... :laugh: