All the above not quite correct. At the risk of being accused of pedantry - is that a form of goat molesting? - ex RM pilots and those from RN/RAF who have done a tour on exchange with AAC are also eligible.
Subject to update, the only written words on the subject I found openly are;
Groundcrew - TA Soldiers
Applicants are not required to have previously served with the AAC. However, if they have no previous service, they will be required to complete all relevant AAC trade training, culminating in a Groundcrewman Class 1 course and either a Signals Class 1 or Driver Class 1 course.
All soldiers wishing to fly in the TA must have qualified previously as Service pilots and served at regimental duty with the AAC or 3 Cdo Bde Air Sqn RM.
Mandatory Training - TA Soldiers - Gazelle Refresher Course
For those aircrew who are accepted for 7 Regt AAC (V) and are totally uncurrent, Gazelle Refresher courses are run at Middle Wallop. In exceptional circumstances the course can be run internally at 7 Regt AAC (V). If the candidate does not pass the course, the Regiment reserves the right to terminate the enlistment process.
7 Regiment Army Air Corps is the only TA Regiment in the Army Air Corps (AAC). The Regiment only recruits former members of the Regular Armed Services. All goundcrew are ex-servicemen, mainly AAC although not necessarily so, while all aircrew will have served with the AAC or 3 Brigade Air Squadron.