If this is a Vauxhall dealer should be fairly stright forward. Next time you take the car in make sure its fully warmed up so the pedal clicks when pressed. When you drop it off ask them to come out so you can show them the problem is there, let them try it. If they still say it's not a fault then ask them to let you try the clutch pedal on another Insignia in stock and see if its the same.
Some more info here:
Some more info here:
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