Insignia glow plug issue

I had a similar thing with my old Citroen C4, but the engine light stayed on and it ran rough, like it was missing a cylinder. Turned out to be a faulty injector. Is the Insignia misfiring or idling rough?

Thanks! No misfires or rough idling, but it takes a bit longer to start, especially when cold. Could it still be an injector even without those symptoms?

Possible, but less likely if you don't have the major symptoms. Mine was shaking like mad! Since you suspect the glow plugs and the light's on, get them checked by a mechanic.

Took it to the mechanic as suggested. Glow plugs were the problem. Cost 440€. Thanks again!