Has anyone got knowledge or experience of a failing or failed turbo?
What were the symptoms?
How did the engine react off and on load?
Might there have been noises to suggest something amiss?
What Fault Codes were there?
Anything that happened can be relevant in diagnosing a possible or potential failure.
I've just found a link for replacement... if anyone's interested?
https://www.landyzone.co.uk/land-rover/how-to-change-turbo-on-a-td4.221780

Thanks.

I have had a few turbo "failures" over the years.
My 806 HDI had a couple.
It suffered lack of boost because the vacuum solenoid that that controls the wastegate failed.
I also had an intercooler failure. This results in loss of boost and hissing noises. This happened twice, once when a hose blew off of the intercooler and another time when the intercooler split along a seam.
I once had an overboost and then the ECU going into limp home mode on my 607 and that was due to a vacuum hose falling off.
On my Jaguar XJ diesel I had a turbo failure a couple of years ago.
The vanes had seized up and the electronic vane controller had seized. This was odd because according to the paperwork this turbo was nearly new, the previous owner had paid over £3000 for a new one.
The symptoms were a lack of power and extreme diesel knock if any attempt was made to accelerate.
At idle it was fine.
This took a bit of head scratching to diagnose. It's a twin turbo car but the outputs of the turbos are Y'd together to go through the intercooler. In the end a diagnostics session showed that all of the air flowing into the engine was going through one MAF sensor (the other showed zero) and thus through one turbo. Swapping the MAFs made no difference. The turbo was effectively blocking airflow.
This resulted in me spending 14 hours outside under the car in January. The turbos are extremely difficult remove on the V6 Jag because they sit in a triangular area between the head, the inner wing and the subframe, steering rack and all access is through this triangular "tube". You get to one end by removing the power steering pump and the other after removing the cat. It was an utter nightmare.

Don't forget the clouds of smoke.
Some turbo failures can make it look like a foggy day. Also, some high pitched noises can be turbo related.

To me clouds of smoke indicate a possibility of failed turbo oil seals and that could be quite dangerous on a diesel due to the risks of oil ingestion and uncontrolled "running on". I personally would be quite worried about running an engine that's doing that. The challenge is telling whether the smoke is coming from the turbo or whether it's a worn injector (which is one failure I have had on the Freelander).