Octavia Scout 2008 PD BMM engine trouble

Hi, apologies if this has been covered elsewhere already-

I've got a 2008 Octavia Scout with the PD BMM diesel engine. It's been fine apart from needing a new dual mass flywheel about a year ago, and leaking oil from the intercooler about six months ago. Both were fixed by in my estimation, competent independent garages. The timing belt was changed 3 years ago, and so was coming up for changing again. The car has 104K on the clock, and does a 40 minute commute across town and back each day (not the best I know). It's always been serviced and has given no trouble other than the two issues mentioned. I did notice it seemed a little noisy ,and mentioned this when it went to get it's MOT (which it has always passed before). 

The garage rang up and said it had what they suspected was a damaged inlet valve, and did not want to run it up for the test without checking the head.

When they removed the head, there was significant damage to the camshaft buckets and lobes.

As I really love this car and the garage believed this would resolve the problem- the head was sent away to a specialist and rebuilt and skimmed. The garage believe the damage was caused by by a timing misalignment.

After getting the car back-it runs very smoothly, much better than before-BUT- at about 2500 rpm the glowplug sign comes on and it loses power. The engine management light then comes on, and sometimes stays on after restart. The garage has tried a forced DPF regen through the OBD interface- this has not worked. The OBD returns code 0665 relating to low turbo pressure. The garage does not have the full VAG diagnostics. The turbo sounds like it is working- and expand the rubber bellows.

I have read on this site that sometimes this problem can relate to a damaged/blocked vacuum pipe from the head to the turbo-does anybody else have any ideas or things to look out for?

My next move will be to go to an independent VAG specialist and see if they can extract more information, and also check the diesel torsion offset values in the ECU.

Any advice gratefully accepted! Can't overstate how good the Scout has been, so any thoughts and opinions on this are very welcome.

Thanks in advance