I had a bit of a go at it at the weekend. Started attempting to dismantle the 405 N/A engine and found I need more leverage for the head bolts, so I'm waiting on new tools for that. I took the inlet manifold off on the ex-405 engine, which was pretty straightforward with the engine out. God knows how I'm gonna do it on the Synergie engine in-place:

Maybe I'll have to get creative like you say.