After messing around with the clutch and seeing how it looked (because it was red and pretty), I got back to the proper tasks and set about removing the flywheel to inspect the rear oil seal. To aid this (more to aid the refitting actually as an impact wrench will remove the flywheel bolts fine) I bought a JAS crank locking tool from autolink.

Crank Locking Tool
Very simple to use this – four bolts connect to where the crank pulley would be, then one of the oil pump to lock it. No more messing around trying to hold the flywheel whilst torquing it up!
With the flywheel subsequently removed I could see what was going on with the rear oil seal.
Nothing too alarming, but definitely not clean! On closer inspection it seemed to be the sealant at fault rather than the seal itself. I removed the seal housing, replaced the seal with a genuine item and cleaned off the sealant/re-applied. I then refitting the housing, which is surprisingly difficult with the sump in situ! Got it in the end but I wouldn’t recommend doing it that way to anyone.
I torqued the flywheel, then the clutch. I had real problems refitting the engine, but then I always do. The problem I have is I’m always too quick to remove the engine and re-centre the clutch when it won’t go together when it’s usually just the angle of the engine and box. In the end, I removed the engine for what felt like the millionth time and refitted it without adjusting the clutch position. It took a few tiny adjustments on the balancing bar to get the engine and gear box to go together but got there in the end.
It’s after this that I paid the price for being clever and leaving the inlet manifold on. It just makes access to the starter motor, engine mount, oil filter and so forth that much harder. I reckon I spent an extra 2 hours fiddling around to save 30 mins of refitting the inlet manifold. Lesson learned on that front.