This particular half-deck coach was built (I believe) in Preston, where George Crellin was based, and it was originally operated by a company associated with the businessman who funded Crellin's exploits. It was registered DCK 111, a Preston issue from October 1949, and ended its days as a school bus with Butters of Childs Ercall, Shropshire.
Around 20 or so coaches to this or similar design were built, based on Guy, Foden, AEC and perhaps other chassis, bodied by various different coachbuilders in various parts of the country. Mann Egerton were one of those builders, and below are a couple of advertisements for their bus.
They were, however, not popular with passengers. In order to keep the height as low as possible, the footwells for the upper deck encroached into the headroom of the lower deck, making passengers feel claustrophobic. Hence only the 20 or so were built and did not remain in service for very long.
I'm happy to say there is one survivor, in a preservation group!
Here are more photos: