Sooooo..... went over to see Rod today, very interesting.
He's got a really great car, a genuine Westfield V8, it has a bit of a back story but essentially it is as new, about 5 miles on the clock and to date has not been through its IVA.
As he originally posted, there were idle issues and so far a solution had not been found. Well, it is now sorted pending a couple of new parts.
The main issue was rich running and stalling once it reached running temperature. It was great when cold.
Anyway to cut a long story short after some initial checking nothing obvious then after a bit of poking about with the DVM we found no power to the O2 sensors so the ECU was thinking it was super lean and so just started dumping fuel in the engine to make it rich so the fuel trim was maxed out. We substituted teh O2 sensors for a couple I had kicking around but no change. A study of the ECU wiring diagram for a Range Rover showed the lambda sensors are powered from the fuel pump relay. Having tested continuity of the wiring back to the ECU we were left with the question why there was no power to the lambda sensors. What we found was somebody had, in the past put the wrong relay in both the Main EFI relay and the Fuel Pump relay so the O2 sensors had no power. I pulled the relay and said "that should have 5 pins on it not 4!"
Swapped the relays for the right type and lambda probes started switching, it ran up to temperature and was absolutely fine with no stalling and a nice steady idle. The lambda sensors on the car were subsequently found to be failing, believed to be because for however long, the engine has been allowed to run very rich which has damaged the sensors. SO........ a couple of new sensors and it should be good to go!
Hopefully Rod will pop back and let us know if this has been a permanent fix and if he gets it through emissions on the IVA test, Good Luck.