I had a similar problem on my last 1.6tdci ((09 reg). There was a brief hesitation during the engine warm up while driving under load IE up hill when the engine was cool, pulling off from a standing start when the engine was cool/warming up. This developed into cutting out under any kind of load IE when the clutch was at biting point, engine would cut. If I started the engine & waited until the engine was warm (about 15mins), the car would run fine, apart from an occasional brief hesitation. I had this checked out 3 times by different garages with no joy aprt from the advice of replacing the injector rail assembly at a cost of around £750, as this was the only consistent area of fault codes. 1 trip to a diagnostic center revealed a faulty solenoid on the said rail assembly which was replaced for £60 sourced from ebay. Perhaps worth checking out?
Good luck, as I can tell you from experience it is a really frustrating problem.