Only realised today that there is a recommended ECO tyre pressure. Normal on my 1.6 TDI is 32psi and ECO is 36psi. I've changed mine to ECO and reset tyre pressure monitor.   No obvious change in ride quality so far. 

If you were to be getting any better economy in the way of using less fuel that would have to be because the extra pressure in the tyres changed the profile and there is less tread on the ground so less friction meaning less traction.

 

In a UK winter do you not want the tyres giving as much traction so steering and braking ability as possible.

They are Summer tyres after all and not that great in the wet let alone in the wet, cold, snow or ice.

I'd happily sacrifice the marginal improvement in fuel economy for additional traction, even if that is equally marginal.