Essex
What you're looking for is called "Lateral Recruitment" (see below)
Recruitment Centre | Defence Jobs
As stated above, it can be a lengthy process but the detail is all laid out on the website. Whilst it doesn't state that squippers are specifically in demand right now it's always worth registering an Expression of Interest so they've got you on file if things change.
Job description for Aussie Squipper here:
Air Force | Aviation | Defence Jobs
Best of luck
Nick