Thanks for everyone's comments...
One Iota...
I think in my case the heat is from the transfer rather than the exhaust. So far, I've found LR will readily rectify any problem, no matter how big, if they can confirm the problem, rather than dodge the issue. MR Automotive tell me the transfer case is the same as the previous model, so I guess it is.
Rick 130...
The oil was Bimrose 75W90, which I believe to be higher end quality, so should have more than met required specs. The oil lab tells me that if dust was the source of Silicon, aluminium would be approximately TWICE the Si reading. As you see below, Al is a mere 1/9th of Si, so they conclude gasket maker is the prime source of Si.
Cu 949; Fe 353; Cr 3; Pb 1; Al 27; Si 251; Sn 54
Yes sometimes lab reports don't show much light on things. It doesn't tell you how much visible, large iron particles are present, and in this case that was significant. But it did raise alarm bells indicating a problem, which is supported by the magnet plug debris. An independent LR mechanic did not pick up the problem, during a routine inspection, so the lab analysis was an excellent step in this case.
B92 8NW...
Yes, I was using our AW10 Antiwear, and it ran a little cooler than before. I could hold my hand on the seat box, although still hot. Initially I could not hold it there for more than 8-10 secs! Unfortunately it won't necessarily fix mechanical problems.
PAT 303...
Actually i have 99,000kms on the vehicle and only 40,000km on this oil, so it would have no run in wear metals in that oil. Occasionally the centre diff lock is activated when firm ground intersects loose stuff, and often gear changes are needed then. That's exactly when the severe driveline clatter takes place...it shouldn't be as violent as it is.
Rick 130...
Transfer running hot: Yeah I think viscosity choice is very much a balance between keeping mechanical friction, or metal to metal wear as low as possible, while also minimizing fluid friction or churning, which is more a problem with the higher viscosity oils. So you need a viscosity that is not too low to cause increased wear, and not too high to churn. At this stage, it appears that the 75W140 has it running cooler than before. A 75W110 may well be a good option as you suggest, but my main goal at this stage is to rectify the cause of the problem under the last 800kms of warranty left.
Cheers
Brid

