Thanks guys for your thoughts.
I agree re looking at power supplies/grounds/chaff/wiring problems on the ECU etc.
I was also going to look at scoping the ignition pack primarys as well.
The other idea I had was to set up my scanner in live data mode, with graphs maybe and monitor various PIDs and see if anything crops up during the moments of madness. I too am wondering about the MAP, could scope it as well.
I thought also trying to do some cranking vacuum tests that would then only be monitoring engine mechanical condition.
The only positive in this is that so far at least its a very consistent fault and will always do it!
I spoke to the local dealer and they claim not to know of any lifter bulletin from Pug. I don't really believe them and my mole in the workshop is currently on holidays.
I'll update you after the next phase.