Td5 Discovery automatic M&S Lights no throttle

[Wings]

My Td5 Discovery automatic workhorse for the past 6 months has had intermittent problems with the M&S lights and loss of power, no set pattern, some times after 100 plus miles of driving, then this morning after 2 miles.

Car has been in to three garages, three parts fitted, three fairly large bills, the fault becoming quite scary, especially with motorway driving. When it happens I can usually keep the car in transmission, put the car into neutral, turn ignition key off then on, engine throttle power kicks in. This morning that wasn't possible, although I managed to limp home.

Spent the past hour trying to sort the M&S lights and get throttle power back, then with my foot fully depressing the throttle peddle, the M&S extinguished and throttle power fully returned. This may be fully coincidental, but with motorway driving, for obvious reasons I need to get the problem sorted. It sounds like a possible electrical problem ECU and/or throttle solenoid, would I be best placed to engage an auto electrician, rather than the attention of a fourth garage.

Incidentally I conducted a diagnostic check, and obtain the following code result,
Driver Demand Supply Fault
Ambient Pressure Circuit Fault