Ha ha Martin.

After all these years of GTA ownership I think I went mad years ago.... but is it the symptom or the cause..?

"But my dear how 'bout you?"
Anyway had a look this again this morning. Front pump is definitely running, fuel filter (or at least one of them - need to check the receipts for the last service is new so that'd be a big lot of crud to gather inside of a 1000 miles) so then had a think about your initial comments plus something Miles mentioned in a note about the TDC.
So.... had a look at the wiring to the TDC. Mine hasn't got the Renault plug on it, it's wired with normal electrical connectors, plus I noticed a small cut in the insulation of one of the wires. I crimped up the connectors tight (squashed 'em with me connector tool) and wrapped some insulation tape around them.
Took it then for a run and so far so good. I'm not sure it's a definitive fix, but I'll take it out again tomorrow and keep close to home but try to do a few loops to test it out. I haven't gunned it yet Martin as when it cuts it's pretty violent so I want to make doubly sure this is a fix first. Then I'll swap back to the updated chip again to see how that works.
So although I don't want to jinx it, Thanks Miles. (I hope)
Change one variable at a time!
Yours from the funny farm.
Darren
I'm just here for the gasoline.