Glow plug light

Glow plugs on these are controlled by control module,
not a relay,
and by temp sensor do you mean the coolant temperature sensor?
so the fact that the lamp light in the morning leads me to suspect a fault in the coolant temperature sensor.
guessing the sensor you changed was for the gauge.

ok I renewed glow plug control / relay(under the battery),4 glow plugs,and a water temp sensor(bought from Vauxhall ) ,when engine is cold the light on dashboard comes on for a second or 2 ,engine fires up instant,once car has been run ,the light now fails to come on for rest of day making it very hard to start,,thanks

Relay control is from the ECU,
Which takes it's control signals from the coolant temperature sensor which then decides if glow control is used or not.
so If everything you changed hasn't altered the glow time I be checking the ECU.
But you'd need Vaux software for that.
the software has a function to activate the relay for test purposes.

ok,thanks ,