the air cadet organisation is flatly refusing to even consider allowing sqns to team up with local civvy gliding clubs
Sorry
Sky Sports - not quite true.
Whilst there may be annoying hoops to jump through (H&S, DBS, ACO orders etc etc etc) a number of units
are teaming up as you suggest, and I know of quite a few more currently being looked at.
It might be difficult to get approval, but the ACO is most certainly
not "flatly refusing to even consider" as you suggest.
If you do have access to/connection with an ATC Sqn, then they can find the exact procedure in ACTO (Air Cadet Trainng Order) #35.
Not an easy procedure to be sure - but not impossible.