Ash,
Unfortunatley there is no good rule for this. The work has to be done with 145 organisation.
I see your 'experience' options as:
Wait til you get out and do 1 year as a "fitter" (If you can get a job).
Work for free (If someone will let you)
Work at night/weekends (If someone will let you)
You are doing the right thing if studying for your ticket now.
Best of Luck
Rigga