I did a bit of looking around and decided I should put some fuel treatment through the engine, I am 99% sure no one would have put any through before so it might make a nice difference.
After searching through the vast array of choices I settled on Comma Diesel Magic, its a one shot usage i.e. you put all of the contents of the bottle into one full tank of fuel (diesel). I had used a similar product in the past on my old car, but it didn't make much difference so I wasn't expecting much.
Luckily when I went and bought it I was about ready for a full tank fill up, so I emptied the bottle into the tank then went round to the pumps and filled up. This should have allowed it to mix in well with the new diesel, rather than sitting on top if I'd have filled up before putting it in.
After doing over 100 miles I can happily say that the stuff has worked er.. magic, the car feels so much smoother, there is no hesitation now when cold at all. So far this tank the fuel consumption appears to be well up on previous tanks. For every quarter tank I'd get around 110miles at best out of it, I just achieved 130miles with the first tank with this treatment in.
I cannot recommend the stuff more highly, at the bargain cost of £6.50, this stuff has made the biggest difference to my car out of any of the changes I have made. I will be putting this stuff in every third or forth tank of fuel from now on, to keep things crystal clear.