307 HDi loss of power and Depollution System fault?

Hi, after 20,000 faultless miles (now at 105K) in my '06 307 SW 1.6 HDi (110) I have experienced a sudden loss of power, inability to rev, strange noise coming from the engine (turbo?) followed by a 'Depollution System Faulty' warning msg and an emission control system warning light!
I was motoring along nicely at 70 when the power suddenly vanished, I pulled onto the hard shoulder and found that the car would still run, but only at very reduced speed and revs (~2500 max), and with an odd noise coming from the engine which increases with engine speed, and I am surmising could be the turbo.. I carried on to my destination, slowly, then returned home, approx 10 miles after this loss the 'Depollution System Faulty' warning beeped as I was struggling up a steepish hill, along with the orange emission control system warning light, which has been on since.
I have read of various problems along these lines, and have so far tried cleaning the fuel cap and nozzle, adding a bottle of redex, taking it for a lengthy high speed burn (difficult when it wont rev above 3000rpm!), all to no avail. The DSF msg appears when I start the car, then goes, and the emission control warning is now permanently on, and the engine whines oddly when revved, or when running above ~1500rpm. The engine starts fine but wont go above 3000rpm when stood, then splutters and starts chucking white smoke out. When moving it struggles to go above 30 uphill, but goes ok downhill, until the revs rise sufficiently...
I have booked the car in for a diagnostic check and lookover but would greatly appreciate any help from the learned people on here as well as to what the problem and possible solutions might be... thanks.

Tone
September 2013