Well after a lot of head scratching and frustration at getting to totally inaccessible sensors and pointless removing of parts just to get access to pretty important service items, I've finally got this fixed now!
The problem of diagnosing this DIY is 'hesitating and cutting out' can be caused by just about any sensor or component in and around the engine, so it is literally a case of going through each step, checking and cleaning each item until you find the one that is causing it.