Got the car back this evening.. Goes like a rocket and seems more "refined" than before. I'm getting 45 mpg at a constant 80mph.
@cjetsy - you were right about the fuel filter. Mechanic changed mine after I mentioned it and it was the original one, was never changed before. It's a bitch of a job due to the location beside rear axle, hence it was never changed previously (took him 2 hours).
All in all I got the egr and attached manifold totally cleaned out, dpf chemically cleaned and regenerated, oil and oil filter changed and the fuel filter changed.
I can honestly say that the car has never run smoother but I will post an update if anything changes...I have a 150 mile trip tomorrow so plan to drive fairly fast to see how it goes.
Another thing, the turbo lag that is common on these appears to have disappeared and I can pull out of junctions etc.. now without having to slip the clutch and rev the arse off it