I have to disagree to an extent.
I have used ASDA, BP and Shell in my current 1.6TDI. Whilst it may not make much difference to reliability, there has been a difference in fuel economy.
Running on ASDA fuel my tank average was around 4mpg lower than with Shell, and BP was 3mpg lower than shell (hand calculated, Millers in every tank). I do between 780-850 miles per tank, so 3/4mpg is a fair difference.
The VPower diesel stuff is hype (as proved by a member on here who ran it for around 10 tanks), but I think in general there are differences in the 'normal' fuel at the pump, and it depends on the additives being added to the fuel. All fuel is the same base, but the additives per company are different, and are added at the pump.
Regarding bio fuel content, I believe Morrisons run at 7%, which is higher than any other
garage. Biofuel is bad for the DPF, so on that basis, I'll be putting as little as the stuff in as possible.