Thought I would post some pics of the shiney bits below as some of the install too Desperately needs a smaller backbox on for full appreciation of those LCA's, but I'm hoping to get a full system made up soon.
If you're satisfied with the checks you've carried out so far.....it may be time to start suspecting the clutch assembly ( a pressure plate breaking up would fit your intermittent symptoms quite well)......fingers crossed it isn't your gearbox
I don't know what the problem was, but on the third run there was a little poof of smoke. I didn't know it was sorted until the drive home. Goes well now though. I'm guessing the cat was blocked, guy said it was the dizzy but dizzy was replaced a few weeks ago