My car just stopped working and a mechanic told.

My car just stopped working and a mechanic told me I would need a whole new ecu unit so we replaced that ie the unit and clocks and key lock but the car starts for a second and cuts out he then told me that I would have to change the glo plugs which I done still the same cuts out after a second. I'm just wondering does the numbers/codes have to match the codes on the old ecu unit? Many thanks nick