I get ~35 every morning in a 5 mile round trip to the nursery (in a VRS) if I got < 40 on a 10 mile stretch I would be either very late or breaking the law.

I have found my computer to be bang on certainly within 5 percent - only the overall trip changes if I hoof it (indeed on the round trip I generally go faster sans child)

Driving style is the biggest changer of MPG - and assuming you don't drive it like a petrol, then tyre pressure and open windows are your likely culprit.

I can get 60mpg on a free-flowing journey as long as it's clear to me that sprinting won't get me along any faster!

This may be a silly question but have you zeroed trip computer #2 since you took delivery.

If it has been at the dealers a while, short test drives, shunted around the yard and left ticking over in the workshop then the mpg figure on trip computer #2 will be really low.  If this is the case then the reason your mpg is apparently improving is because you are pushing the average up by driving it normally. 

 

I am halfway through my 3rd tank full with my 1.6 TDi - 1st tank was 54mpg brim to brim, 2nd tank was 58 mpg brim to brim. 

I've zeroised everything, I've come to realise my driving style to and from work on such a short journey may not have been as economical as I thought. I now drive like miss daisys chauffeur I to be honest the difference in time is very little 

I've zeroised everything, I've come to realise my driving style to and from work on such a short journey may not have been as economical as I thought. I now drive like miss daisys chauffeur I to be honest the difference in time is very little 

Don't drive it like that all the time.  A good hard "drive-it-like-you-hired-it" around the B roads in 3rd and 4th may dent your immediate economy figures but does wonders for cleaning out the carp that builds up in the EGR and turbo.  That improves overall performance and long term economy.

Yep been told that before thanks, I can't wait to drive like  that again lol 

The occasional "Italian tune up" does a lot of good for your car. Not only does it help burn off coke deposits from the exhaust (especially if you only do short journeys) it improves your mpg and emissions (good for mot time) but will help free up binding brakes by putting them through a good heat cycle.

Also from my own experience fresh air filter makes a massive difference. Fresh oil also helps. In general good servicing is money well spent.

Additionally the brand of fuel can make a big difference. A petrol nissan I had used to do and extra 30 miles a tank on shell over most other brands and about 20 less on Total. This was over that same 120 commute.

For reference my vrs does about 30 on my current 16 mile daily commute, my previous zafira B 1.9cdti 150 did 37, an omega 2.5 v6 about 25, the good lady's micra 1.6 about 40 and a friends 200k S reg octavia 90 bhp 1.9tdi estate a whopping 58.