As far as I know there is no set criteria for unlicensed mechanics.
Generally at my carrier (BA) mechanics need some for of Apprenticeship or recognised trade qualification. Other than that i's just general experience in fixing things. I know guys who've gone straight from college into mechanic and others who hold a B license modules with x years experience.
I'd suggest staying and getting a license through the forces if possible but of course if you don't wish to, I'd say you're pretty set up already for mechanic.
Safe flying
Tech_Log