Had same problem with my corsa lite. Plug port No. 2 not firing.
Had new coil installed last Friday. Wednesday this week, same problem.
Took back car to the dealer and was told that it was probably a faulty coil pack. Asked them to please check plug leads as I was told that if the plug wires were faulty that it fires back into the coil pack and damages it.
Yesterday had new coil pack and a set of new plug leads replaced.
So I hope this sorts out the problem.
Have you checked your plugs to see which one or two are not firing?
Been told that 1 and 4 plugs work together and 2 and 3, so you may find that there is more than one plug that is not firing, but not necessarily so.
Other reasons for coil pack going are :bad earth and alternator over charging. Ask for a diagnostic test if necessary.
The coil pack seems to be an achilles heal with the corsa lites.
Hope this helps
Heather