the ECU on the later model is on the right hand end of the block with 2 big plugs going to it, maybe a sensor failed - crank sensor is a common one - hard to find at back of block look for it from underneath - below starter motor i think,
new ECU is £450 or there abouts sensors about £35.
garage wont give you much change out of a grand.
scrapping it works out cheaper!
Are you using the correct key?
Corsa has a system like FORD PATS, where the key has to operate the sensor around key barrel .. and activate the ECU.
What did you replace exactly?