Thanks all for the replies to my question, I got the job finished off on Saturday, used 3Bond, so far so good. I actually discovered a tin of Hylomar on the shelf that I had forgotten about, but it had dried out quite a bit so I wasn't confident that it would still be any good. Wonder if anyone knows a solvent that this can be rejuvenated with? Expensive stuff to throw away.
I'm interested to try the silver paint thing, but I was not confident of this method in something with two independent angled faces like the V8 inlet manifold, and given that is such a pain to pull down again I thought I might try this technique on something else at a later date- sounds ideal for, say, a water pump, timing cover or oil pump.
I have to repeat this whole task on my other rangie soon, the 4.4 with 3.5 EFI manifold- there's coolant leaking somewhere in there, dunno yet whether it's the manifold gasket or the heater hoses. Ho-hum.