The first time my EGR valve didn't show up any faults when i took it to the dealers for warranty fix. They rang me up telling me it was fine and i'd asked them if they'd driven it. "Eeeeer, no". Half an hour later there were fitting a new one
That was with the car a year old with 15k on it. It also happened again recently but I sorted it myself.
The problem is the egr valve is stuck open, causing a drop in exhaust gas pressure and therefore not spooling up the turbo at low revs.
Your first point of call is to block off the EGR valve which is a 5 min job. If this solves the problem, unblock it then take it back the dealer and ask for a new one (if under warranty), or buy a reconditioned one off ebay for £25 and fit it yourself.
The valve is located on the right rear of the engine at the top (looking from front). Its only held on by 6 bolts, so undo those, cut a thin piece of metal (i saw an example with a sardine tin lid) to match the shape of the gasket from the exhaust, and bolt it up again.
If it feels like the car has power from low revs then you know what the problem is.
EDIT: Just noticed you're not far away so if you're having any difficulty give me a shout!