Oh what joy! Turbo on, turbo off. Manifolds on, manifold off. Camshaft on, camshaft off. Mount on, mount off. Tensioner on, tensioner off. Cambelt on, cambelt off and so it goes.
Having said that, today was a fine day if a little too short daylight-wise. After discovering the cambelt wanted to wander off the pulleys, I turned my full attention to that, forgetting to reset and relock the timing bolts etc. when I whipped the cambelt off
As per Jim's advice, off came camshaft again to get the crankshaft locked, then refitted cam and aligned the pulleys, the belt went back on and four engine rotations later all looked well, at last. There is now some difficulty getting the crank pulley back on but I suspect that's due to the extra layer of corrosion that's formed on the crank tail. Hope to sort that tomorrow.
For the record, I used a metre-long brass rod for the flywheel locking tool in the hope that I could reach and turn the engine with one hand and insert the locking rod with the other but I made a chance finding that was an even better one-man strategy! Owing to the extra length weighting the other end, I found that, in the shape I made it and as long as the tip is in the block hole, it will self-insert as soon as any flywheel hole presents itself. It inserts itself into the wrong holes if you're not careful, which gave me palpatations thinking I'd struck valves to piston. Seems you were right citrojim, the XUD's do have additional holes in the flywheel.
Another bodge I might patent

is the cambelt tension plunger locking pin. After compressing the plunger fully into it's recess, I drilled a 2mm hole through the casing and through the plunger into which I inserted a small tack pin. This pin held the plunger well out of the way as the cambelt assemblies were refitted oh so easily this time.
All in all, I feel quite experienced at XUD cambelts now.