Ford Fiesta 1.4 TDCi 68 Zetec Review

Well I've had this car a few months now, it's a Ford Fiesta Zetec 1.4 TDCI on a 54 plate. I've owned a diesel Fiesta before (a 1.6 Zetec S TDCI) and I was very very happy with it, commuting 150 miles a day in it. I suppose I'm relatively happy with this, but my major gripe is the MPG. I bought this on starting a new job as I now have to drive 40 miles each way. All the literature points to 54mpg as the minimum, which sounded great to me and the overriding afctor in deciding to buy it. I'd previously been driving my Honda S2000 or MG ZS+ 180 to work - both very juicy! However, as a few other people have commented, I'm not getting near this figure! My journey goes like this - about 5 miles on B roads at about 40mph, then 10 miles on A roads at around 70mph, with a roundabout and a few speed cameras, then I hit traffic for about 3 miles which takes about 15 minutes to move through. Then it's on to the M25 and about 16 miles between 50 and 70mph (on a good day). 5 miles with traffic, traffic lights and a roundabout travelling between 5 and 50 mph. Then into Watford and the final leg of about 2 miles at 10 mph round the one way system. In my mind, that's combined mileage which I should apparently be getting about 64mpg. The reality is I'm getting about 45mpg for that. I'm very conscious of reving and my driving style too, so I don't think it's becuase I'm used to driving an S2000! Very VERY dissapinted with the fuel economy, but overall, a solid, good looking little work horse.