Henk.
To pick up where Rigga left off...some operators on my side of the pond use various formulas to man their operations. And as Rigga mentioned is totally dependent on type operation, location, etc.
For one, will the same mechanics comply with the line and base maintenance at the same location? Or, will these be separate locations?
Too many variables to give a better answer. Plus things are a little different on your side.
But to get you going on that size aircraft, the basic formula for line maintenance is either one mechanic per engine or 1.5 mechanic per airframe. This would also cover on site major component changes.
Good luck.
W1