Nippymog, I just wondered if one of the leads improved when hot. I know it’s a long shot but if the diagnostics isn’t picking it up then it sounds like something at the end of the process and physical?
I once owned an AH Sprite that would not start or if it it did start when in the cold damp air of our beach community it would run very ragged until it got warmed up.
I found the problem when trying to start it ( someone else using the starter) while observing the wiring in the dark. There was arcing coming from degraded insulation and hairline cracks (invisible to naked eye) in the plastic parts. The UK can get pretty damp so it might be worth a check.
