Engines, you said:
"2010: Control of VGS moved from HQ ATC to 1 EFTS
2011: No.1 EFTS absorbed into No.3 Flying Training School
2014: Gliders handed over from 3FTS to newly formed 2FTS"
That however was for the operations aspects: flying, instructing, airfield operations etc. Control of the engineering and logistics remained firmly with HQ Air Cadets under the control of SO1 Eng & Logs who is a civil servant (although he was always referred to as a Wg Cdr). HQ Air Cadets continued to own the engineering and logistics contracts; SO1 Eng & Logs was the Designated Officer for the contracts and it was he who owned the Quality Assurance and contract monitoring roles. He was therefore responsible for all engineering standards. The Project Team (Viking, Vigilant & Tucano) were responsible for airworthiness.
In the beginning though, the T21s etc and then, initially the Vikings were registered with the BGA and maintained to BGA (and CAA) standards. This changed sometime in the 90s to the present system.