Nicely done.

 

Was it all down to the bad transistor?

yup! it was! Changed the transistor and it worked like a charm!

I understand the coil (ignition coil) has a primary and a secondary (although the primary may be a tapping on the secondary). The output of your circuit would presumably connect to the primary and initiate rapid switch off or interruption of the current through this coil. The back EMF thus produced is 'stepped up' by the secondary (difference in turns ratio) to provide sufficient voltage to cause a spark to jump across a suitable gap.

 

But l not sure the driving transistor would firstly be able to withstand the primary voltage spike (60 volts is its limit I believe). And secondly the capacitor C1 may well moderate (slow down, round off or whatever word one cares to use) said voltage spike to a point whereby the induced voltage from the secondary may just be a bump and not a spike!

 

I further understand that commercial electronic ignition systems more often than not use a thyristor as a coil switching device.