2005 2.0 turbo not kicking in. *previously posted in common prob thread*

[zeezee]

This was posted in the common problem thread but I decided to give it its own post, for further posts.
I have a 2.0 diesel 2005, which I have had for about a year.
It has been a pain in the butt.
Most recently, last July, it started losing power to the point of running flat, no turbo. It went to the mechanic and got its solenoids changed (scrapyard doner), a new downpipe and cat.
Has been fine since until a few weeks ago when I felt it lose power suddenly. I rev'ed it a bit and it seemed to be fine so I thought it was my imagination. A few days later my OH was driving and said the turbos weren't spooling up. Again, revved it up a bit and it seemed ok again.
It has rapidly gotten worse since, permanently running flat, in and out of limp mode, shaking and just feeling wrong. Engine warning light, code P0047.
I don't know if it is relevant but I also recently started hearing turbo whistle, while it seemed to be driving ok. I admit to being generally oblivious to things like that I def think it didn't use to whistle
As far as I am aware, it does not have a DPF. We did verify this with a mechanic last year.
**
Car went to the mechanic a wee, who had it a week.
At first, he said it was working fine. He sent someone else out on a test drive and they said it had no power. He got in it again and for him,  it worked fine. It sounded like a scene from a comedy.
The next morning it lost power on him. 

**
We got the car back this morning. I don't actually know if he did anything to it other than drive it around a bit. He doesn't know where to start with it and suggested taking it to a Ford garage. As it seems to work after turning it off and on again, he doesn't think it was the turbo itself.
What sort of cost am I looking at, taking it to Ford?
Realistically, what would I expect to get for it if I were to get it fixed, fully working? 111000 miles, cambelt was done last year - I think. Fairly good service history.
On the flip side, if I sold/PX it as is, what would I get for it selling it as faulty?
 

[isetta]

https://www.autoblog.com/2016/03/25/p0047-obd-ii-trouble-code-turbo-super-charger-boost-control-sol/?guccounter=1

this describes some causes/things to check. I can't verify how good that info is.

But if this was my car I would be checking the stuff it suggests (hoses / connections etc).   I do not know if this has a variable vane type turbo or a fixed vane turbo with wastegate.

From the intermittent nature it sounds like something that is a simple rather then major work fix once identified where it is exactly. the identification being the problem.

I would be reluctant to take it to a Ford dealer.  I would think an independant business who specialises in turbo diesels would be better, but finding one, particularly one on personal recommendation is trickier. Hoping the expert will say, yes I know what that will be and going straight to the dodgy wiring connector or whatever.