Nice one Geo.
Yes, from about the period your Sqn got Lancs, the cockpit area, visible beneath the canopy, was matt black, as was the bomb aimer's compartment in the nose. This often continued aft, to the main spar, although the radio op and nav stations sometimes remained at least partly in the green-grey colour.
Note that this colour is RAF Cockpit Grey Green, a sort of sage green colour, as seen on Spitfires etc, and not the green yellowish Interior Green used on American aircraft.