ECW world file states the X and Y coordinates of the centre of the north-west pixel. This file is available as a downloadable zip archive from the OS MasterMap Imagery Layer product page.
JPEG world file states the X and Y coordinates of the centre of the north-west pixel. This file is available as a downloadable zip archive from the OS MasterMap Imagery Layer product page.
The XML schema for OS MasterMap Imagery Layer is available to be downloaded from the OS XML file resources page under the OS MasterMap layers heading.