(T) Check Glow Plugs Warning (plugs have been replaced)

Hi
Can anyone help please? I've got a punto 1.3multijet and have a bit of a problem
The check glow plugs warning came on so i had the plugs replaced but the warning is still on!
Since the plugs have been replaced it takes the car two attempts to start from cold, after its been used a couple of times in the day it starts first time. (before they were done it started and drove fine just had the warning message)
Took the car to Fiat yesterday and was charged £90-odd pounds for them to say theres nothing wrong but come back and have a full wiring check at a cost of £145 and that might find a problem (The message is still on)
Is there anything else i could check before resorting to spending loads of cash on it?
Thanks

Could be the relay.

on start up do u let all the lights on the dash go off before you fully start it.

did it work correctly before you had the glow plugs changed e.g. started first time. if so i would take it back to the garage you had them done and get them to sort it.

try disconnecting the battery for 10 mins to reset the system.

Disconnecting the battery will not clear faults from the ECU.