Redtail - to answer your q, this is the U.K. system:
Mechanic:Non - certifying posn, tho' most companies grant "limited & simple" authorisations to cover daily checks & some component changes,i.e.wheels/brakes/filaments etc.
Within B.A. this posn is a "technician". They can hold approvals that cover more component changes but not function checks or trouble shooting (Ramp Maint Auth), or that cover a complete zone during hangar checks (Base Maint Auth).
Engineer (sometimes refered to as "Licenced tech"):Certifying Engineer, holding Licences & company approvals, signs for work up to the limit of their licence (airframe/eng/elec/isnt/radio etc).May be hands on or not dependant on Company & whether line or base maint.