I've had my 2.5 td (manual) for a few months now and I'd agree I was utterly disappointed with the sluggishness of the car. It wasn't inspiring at all, In fact I was g to move it on because it felt I couldn't hack how hard work it was to drive.
After a full service and some addition of diesel treatment I noticed very little difference.
And thought the only way I can remedy this is with a chip tune. Now I phoned a few local tuning centres and they couldn't get hold of the chip set needed to tune this car.
but I was given a number for a lad who does the chips for these.
I got a chip off him and my car is a world away from what I started with.
It boosts and pulls from around 1500 rpm. Rather than 2500 and i would recommend this route without hesitation. How ever you need to find someone who is willing to unsolder your chip and resolder a dill socket in to your ecu. Once this is done I'm sure you'll be a lot happier.