Hey guys!
I have an update and some great news!
My baby is back, sorted and better than ever!!
This epic saga has dragged on longer than it should by a poor ECU tester and repair 'experts' - who sent back the ECU saying they could find no faults, despite there being black scorch marks inside! So we went back to square one and went through everything again, and also paying attention to everything in the service manuals, but we kept coming back to the same conclusion - it must be the ECU.
So I took a punt and risk on a cheap one selling on FleaBay, which arrived mid-week - we put it on and there was an immediate improvement and difference! Now we knew we back on track and close to the finish line, so doing some more electrical testing we were able to see clearly some final minor problem areas - replaced the ignition coil, some wiring that had seen better days, battery connections (*** note that was missed stupidly, don't forget to look at this if you have similar problems - easy to forget! doh! ***), further cleaning on various sensors and air flow meter, and voila! Working as it should! And seemingly much better than before!
Not only does it now start on the button (no need to hold the key in and dipping the throttle to help it - although if very hot I might still have to), but it also drives a LOT more positively and tightly [

] Idles smoothly and sits tightly on 800rpm. Plus some lights on the dash that weren't working - are now!
So there you go guys. Definitely ECU related and ignition coil had seen better days, we did do an awful lot on this so maybe other things that were replaced/improved prior to the new ECU needed to be done but we don't know now.
For the benefit of anyone else coming across this topic now or in the future....
**** Do you think driving it with a knackered alternator caused all these problems? Therefore, if your alternator goes DO NOT DRIVE and risk it? ****
I'm interested to know.