Right 99.9% sure I've got it sorted now...
After working on it over the weekend and again disconnecting the CAM sensor, it still had issues of slow to crank...hmmm not the same result as before, so definitely not the ECU then...Damn.
Femi turned up with a spare battery today. So fitted that and ran the car for almost 2hrs...car starting a dream...no issues. Battery holding 12.7-13.3V. My old battery was at best only at 12.1-12.3V. Apart from taking the car on a run to give it proper testing, I'm now pretty confident issue solved...
I reckon that the old battery although holding a decent charge was not giving out sufficient cranking amps due to degradation. My old battery had been run flat a few times over the past 2 years and gel batteries don't like that too much... So fingers crossed, all ready for Scotland. Just need to find some snow chains to fit now