Beags & Tuc
The SI says (para 1.3.7)
QinetiQ contracted the service through a Framework Agreement with a third party, Command Pilot Training (CPT) Ltd.... CPT Ltd further sub-contracted the service to the PIC, who sourced G-YAKB from its private owner.
According to the CAA's GINFO, that owner is Martin Jeffery Gadsby, and his address is given.
PS Ever thought of the Diplomatic Service as a career, Beags?