OK, got it running and it ticks over fine but when you out it under load it just flats and cuts out. I assume it's either throttle position sensor or compression, hope its the former...Any thoughts obviously welcomed..Ta.

Sounds like it could be fuel starvation. might be worth changing the fuel filter. fuel pump blocked or on its way out maybe. if the fuel tank is quite empty try filling it up a bit. always start with the simplest things first  '04 td6 se
'63 land rover s2 200tdi
'04 mk indy kitcar bike engine

Run "clean fuel" and or injector cleaner for a bit. But definitely change all the fuel filters. MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

Ok, Been told it may be a new engine...I got it wrong on the start thing. it won't start on the key and will only start when the cylinders are oiled and the relay out, plug the relay in when it's going and she tick away but stalls underr load then won't restart..
Being looked at by BMW guy today apparently but not looking good thing

There is a Dutch guy on here searching for a new engine as well. His seems to have suffered from too few kms, no proper warm up etc. Maybe worth looking at his post. I suggested to him to find a good engine refurb company that does BMW engines. They should be able to get it in tiptop shape in not time for reasonable money.

Did the mechanic do compression testing on all 8 cylinders ? MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!