I had this exact problem with my 2.0 TDCI (which I know is a different engine) took it to a mechanic and told him it was the injectors, they did a leak off test and said it wasnt, charged me new filter etc and off I went. Same thing happened, to it to a different garage, said I thought it was the injectors, explained about the last place, and they checked the injectors again and BINGO dodgy injector! But because I had been driving it with a dodgy injector for so long, the fuel pump was also knackered.

So I'd say 99% sure it is 1, if not more, of your injectors.