Chris Osment wrote:A variation on this theme perhaps would be the non-knee frame installed in the old Porters Room at Corfe Castle in BR days.
Not really a variation - as has already been pointed out there was no consistent use of frame type.
Chris Osment wrote:However,going back to the booking-office examples, was it not more usually the case that these frames were not actually installed IN the BO, but rather in front of it and then the BO extended out around it?
Not so - as has already been pointed out there was no consistent arrangement.
I respectfully refer you once again to http://www.signalbox.org/gallery/s/martinmill.htm for an example that illustrates both points.