Not quite the same problem but my 2011 TDV8 came up with Turbo Actuator Fault message and went into limp mode. My local independent said the fault was on the secondary turbo and reset it (FOC). Suggested rather than changing the turbo, see how it goes and replace if recurs. I had a lot of long distance trips coming up so decided to change it but they couldn't get me in for 4 weeks.
The Main dealer said they could do the following week and it would take a couple of days. After 2 days they had not done it (but charged me £170 for diagnosis) and told me both turbos would need changing as the fault on the secondary turbo will have worn out the other on even though the car hd only been driven about 80 miles and never exceeded 2000rpm. I told them this was unlikely to be the case and took the car away. I have done about 70,000 miles over the following 5 years without a single turbo issue and saved myself about £9k.
The moral of this story is never trust people that lie to you and charge you for unnecessary work. In short, never trust a Main Dealer.